Callum here, I was the developer that first discovered and reported the litellm vulnerability on Tuesday.
I’m sharing the transcript of what it was like figuring out what was going on in real time, unedited with only minor redactions.
I didn’t need to recount my thought process after the fact. It’s the very same ones I wrote down to help Claude figure out what was happening.
I’m an ML engineer by trade, so having Claude walk me through exactly who to contact and a step by step guide of time-critical actions felt like a game-changer for non-security researchers.
I'm curious whether the security community thinks more non-specialists finding and reporting vulnerabilities like this is a net positive or a headache?
Looks like we discovered it at essentially the same time, and in essentially the same way. If the pth file didn't trigger a fork-bomb like behavior, this might have stayed undiscoverd for quite a bit longer.
Good thinking on asking Claude to walk you through on who to contact. I had no idea how to contact anyone related to PyPI, so I started by shooting an email to the maintainers and posting it on Hacker News.
While I'm not part of the security community, I think everyone who finds something like this, should be able to report it. There is no point in gatekeeping the reporting of serious security vulnerabilities.
> If you've identified a security issue with a project hosted on PyPI
Login to your PyPI account, then visit the project's page on PyPI. At the bottom of the sidebar, click Report project as malware.
The existing account to report is an unfortunate obstacle. Presumably not a huge deal if you were auditing code for vulnerabilities, but still an annoyance.
The threat actor was sophisticated enough to spam GitHub issues with dozens of different accounts. I imagine they could completely overwhelm PyPI with unauthenticated reports.
The best part was that I didn't even mean to ask Claude who to contact! I was still in disbelief that I was one of the first people affected, so I asked for existing reports on the assumption that if it was real I definitely wasn't the first.
The fork-bomb part still seems really weird to me. A pretty sophisticated payload, caught by missing a single `-S` flag in the subprocess call.
As a sometimes peripheral and sometimes primary program manager for vulnerability disclosure, for companies you nearly can't avoid, $0.02 follows.
It's a signal vs noise thing. Most of the grief is caused by bottom feeders shoveling anything they can squint at and call a vulnerability and asking for money. Maybe once a month someone would run a free tool and blindly send snippets of the output promising the rest in exchange for payment. Or emailing the CFO and the General Counsel after being politely reminded to come back with high quality information, and then ignored until they do.
Your report on the other hand was high quality. I read all the reports that came my way, and good ones were fast tracked for fixes. I'd fix or mitigate them immediately if I had a way to do so without stopping business, and I'd go to the CISO, CTO, and the corresponding engineering manager if it mattered enough for immediate response.
I’ve found Claude in particular to be very good at this sort of thing. As for whether it’s a good thing, I’d say it’s a net positive - your own reporting of this probably saved a bigger issue!
We wrote up the why/what happened on our blog twice… the second based on the LiteLLM issue:
I've heard stories lately of open source projects being inundated with vulnerability reports and PRs. But in this case, it seems like AI assistance was clearly a boon for root-causing and reporting this so quickly.
Fantastic write-up and thanks for sharing! I'm sure we will continue to see more of these types of deep supply chain vulns. I think this is valuable for the security community. Remember that Cliff Stoll was an astrophysicist turned sysadmin for Lawrence Berkeley Labs who chased down a $0.75 accounting discrepancy to identify a foreign espionage operation.
Not a security researcher, but this is IMHO obviously positive that the other side of the arms race is also getting stronger, and I would argue it's stronger than on the bad guys' side, due to the best being somewhat responsible and adding guardrails.
I’m a big proponent of it within our company! CC tried to style it to blend in with our blog but it was kind of a disaster. Definitely had a new appreciation for the out-of-the-box experience.
I also tried to include the individual sub-pages of Claude investigating but it really trawled my whole machine looking for malware. Don’t know if you’ve thought of any systematic ways of redacting the endless pages of detailed logs?
At this point I'd highly recommend everyone to think twice before introducing any dependencies especially from untrusted sources. If you have to interact with many APIs maybe use a proxy instead, or roll your own.
GitHub, npm, PyPi, and other package registries should consider exposing a firehose to allow people to do realtime security analysis of events. There are definitely scanners that would have caught this attack immediately, they just need a way to be informed of updates.
It is not effective if it just takes a simple base64 encode to bypass. If Claude is trivially able to find that it is malicious then Pypi is being negligent.
The package in question was live for 46 minutes. It generally takes longer than that for security partners to scan and flag packages.
PyPI doesn't block package uploads awaiting security scanning - that would be a bad idea for a number of reasons, most notably (in my opinion) that it would be making promises that PyPI couldn't keep and lull people into a false sense of security.
I realize this is controversial (and many Python folks would claim anti ethical). But I keep wondering if requiring a small payment for registering and updating packages would help. The money could go to maintaining pypix as well as automated AI analysis. Folks who really couldn't afford it could apply for sponsorship.
If pypi charges money, python libraries will suddenly have a lot of "you can 'uv add git+https://github.com/project/library'" instead of 'uv add library'.
I also don't think it would stop this attack, where a token was stolen.
If someone's generating pypi package releases from CI, they're going to register a credit card on their account, make it so CI can automatically charge it, and when the CI token is stolen it can push an update on the real package owner's dime, not the attackers, so it's not a deterrent.
Also, the iOS app store is an okay counter example. It charges $100/year for a developer account, but still has its share of malware (certainly more than the totally free debian software repository).
Very much not speaking for the PSF here, but my personal opinion on why that wouldn't work is that Python is a global language and collecting fees on a global basis is inherently difficult - and we don't want to discriminate against people in countries where the payment infrastructure is hard to support.
Plus a small fee wouldn't deter malware authors, who would likely have easy access to stolen credit cards - which would expose PyPI to the chargebacks and fraudulent transactions world as well!
Would you happen to know where the latency comes from between upload and scanning? Would more resources for more security scanner runners to consume the scanner queue faster solve this? Trying to understand if there are inherent process limitations or if a donation for this compute would solve this gap.
(software supply chain security is a component of my work)
He said, "pypi doesn't block upload on scanning"; that's part of where the latency comes from. The other part is simply the sheer mass of uploads, and that there's not money in doing it super quickly.
I agree that's a bad idea to do so since security scanning is inherently a cat and mouse game.
Let's hypothetically say pypi did block upload on passing a security scan. The attacker now simply creates their own pypi test package ahead of time, uploads sample malicious payloads with additional layers of obfuscation until one passes the scan, and then uses that payload in the real attack.
Pypi would also probably open source any security scanning code it adds as part of upload (as it should), so the attacker could even just do it locally.
I suppose my argument is that pypi could offer the option to block downloads to package owners until a security scan is complete (if scanning will always take ~45-60 minutes). Our org scans all packages ingested into artifact storage, and would continue to do so, but more options (when cheap) are sometimes better imho. I agree it is "cat and mouse" or "whackamole."
So I've been thinking about this a lot since it happened. I've already added dependency cooldowns https://nesbitt.io/2026/03/04/package-managers-need-to-cool-... to every part of our monorepo. The obvious next thought is "am I just dumping the responsibility onto the next person along"? But as you point out it just needs to give automated scanners enough time to pick up on obvious signs like the .pth file in this case.
It is in a sense dumping responsibility, but there’s a legion of security companies out there scanning for attacks all the time now to prove their products. They’re kind of doing a public service and you’re giving them a chance to catch attacks first. This is why I think dep cooldowns are great.
I feel like they should be legally responsible for providing scanning infrastructure for this sort of thing. The potential economic damage can be catastrophic. I don't think this is the end of the litellm story either, given that 47k+ people were infected.
As I recall, the initial vulnerability in Trivy was introduced by some clawbot. The article author has 5 Claude instances running.
Maybe the author correctly praises the research capabilities of Claude for some issues. Selecting an Iranian school as a target would be a counterexample.
But the generative parts augmented by claws are a huge and unconditional net negative.
Probably one of the best things about AI/LLMs is the democratization of reverse engineering and analysis of payloads like this. It’s a very esoteric skill to learn by hand and not very immediately rewarding out of intellectual curiosity most times. You can definitely get pointed in the right direction easily, now, though!
I’ve entertained myself with CTF walkthroughs on YouTube before and had been meaning to try it out. But yeah I feel it falls under the same category as lock picking, fun to LARP, unlikely to stumble across in my day job.
Thats the thing, i noticed it almost instantly when trying to install a package that depended on it, as soon as it started, it hard locked my laptop, didn't get to infect it.. but if they had slowed down that fork bomb.. it would have done more damage.
Yeah, and this is a pattern I saw in the Fancy Bear Goes Fishing book, a lot of discovery of malware is either pure luck, or blunders from the malware developers. https://en.wikipedia.org/wiki/Fancy_Bear_Goes_Phishing
> Where did the litellm files come from? Do you know which env? Are there reports of this online?
> The litellm_init.pth IS in the official package manifest — the RECORD file lists it with a sha256 hash. This means it was shipped as part of the litellm==1.82.8 wheel on PyPI, not injected locally.
I just finished teaching an advanced data science course for one of my clients. I found my self constantly twitching everytime I said "when I write code..." I'm barely writing code at all these days. But I created $100k worth of code just yesterday recreating a poorly maintained (and poor ux) library. Tested and uploaded to pypi in 90 minutes.
A lot of the conversation in my course was directed to leveraged AI (and discussions of existential dread of AI replacement).
This article is a wonderful example of an expert leveraging AI to do normal work 100x faster.
If it took 90 minutes + a Claude Code subscription then the most anyone else is going to be willing to pay for the same code is... ~90 minutes of wages + a Claude Code subscription.
Ofc the person earning those wages will be more skilled than most, but unless those skills are incredibly rare & unique, it's unlikely 90 minutes of their time will be worth $100k.
And ofc, the market value of this code could be higher, even much higher, the the cost to produce it, but for this to be the case, there needs to be some sort of moat, some sort of reason another similarly skilled person cannot just use Claude to whip up something similar in their 90 minutes.
This is presumably because libc just doesn't change very often (not meaning code changes, but release cadence). But the average native software stack does have lots of things that change relatively often[1]. So "native" vs. not is probably not a salient factor.
> While xz is commonly present in most Linux distributions, at the time of discovery the backdoored version had not yet been widely deployed to production systems, but was present in development versions of major distributions.
Ie if you weren’t running dev distros in prod, you probably weren’t exposed.
Honestly a lot of packaging is coming back around to “maybe we shouldn’t immediately use newly released stuff” by delaying their use of new versions. It starts to look an awful lot like apt/yum/dnf/etc.
I would wager in the near future we’ll have another revelation that having 10,000 dependencies is a bad thing because of supply chain attacks.
This is the security equivalent of having a better lock than your neighbour. Won't save you in the end but you won't be first. Then again, yours could also be broken and you don't get to tick of that audit checkbox.
your link disproves your claim. no naive app depended on xz version >= latest. Most sane distros take time to up-rev. That is why the xz backdoor was, in fact, in NO stable distro
I don't think it does; I think the industry opinion on xz is that we got lucky in terms of early detection, and that we shouldn't depend on luck.
(I don't know what a "sane" distro is; empirically lots of distros are bleeding-edge, so we need to think about these things regardless of value judgements.)
From experience, a lot of people using a "stable" distro are just bypassing that distro's stability (read: staleness) by installing nightly things from a language ecosystem. It's not clear to me that this is a better (or worse) outcome than a less stable distro.
Native code still have plenty of attack surface. If you do everything through pip/npm you might as well publish your root password, but pretending a clean C build from source makes you safe is just cosplay for people who confuse compiler output with trust. If anything people are way too quick to trust a tarball that builds on the first try.
100% with you. Anything that builds from the first try is 100% malicious. No real software builds without 5-30 tweaks of the makefile. And anything on npm/pip is malicious with a fixed chance that you have no control over, as seen in this attack.
But the data remains: no supply chain attacks on libc yet, so even if it COULD happen, this HAS and that merely COULD.
Native software? You mean software without dependencies? Because I don't see how you solve the supply chain risk as long as you use dependencies. Sure, minimizing the number of dependencies and using mostly stable dependencies also minimizes the risk, but you'll pay for it with glacial development velocity.
> Do you think supply chain attacks will just get worse? I'm thinking that defensive measures will get better rapidly (especially after this hack)
I think the attacks will get worse and more frequent -- ML tools enable doing it easily among people who were previously not competent enough to pull it off but now can. There is no stomach for the proper defensive measures among the community for either python or javascript. Why am i so sure? This is not the first, second, third, or fourth time this has happened. Nothing changed.
Not only do the tools enable incompetent attackers, they also enable a new class of incompetent library developers to create and publish packages, and a new class of incompetent application developers to install packages without even knowing what packages are being used in the code they aren't reading, and a new class of incompetent users who are allowing OpenClaw to run completely arbitrary code on their machines with no oversight. We are seeing only the tip of the iceberg of the security breaches that are to come.
I didn’t need to recount my thought process after the fact. It’s the very same ones I wrote down to help Claude figure out what was happening.
I’m an ML engineer by trade, so having Claude walk me through exactly who to contact and a step by step guide of time-critical actions felt like a game-changer for non-security researchers.
I'm curious whether the security community thinks more non-specialists finding and reporting vulnerabilities like this is a net positive or a headache?
Good thinking on asking Claude to walk you through on who to contact. I had no idea how to contact anyone related to PyPI, so I started by shooting an email to the maintainers and posting it on Hacker News.
While I'm not part of the security community, I think everyone who finds something like this, should be able to report it. There is no point in gatekeeping the reporting of serious security vulnerabilities.
https://pypi.org/security/:
> If you've identified a security issue with a project hosted on PyPI Login to your PyPI account, then visit the project's page on PyPI. At the bottom of the sidebar, click Report project as malware.
The fork-bomb part still seems really weird to me. A pretty sophisticated payload, caught by missing a single `-S` flag in the subprocess call.
It's a signal vs noise thing. Most of the grief is caused by bottom feeders shoveling anything they can squint at and call a vulnerability and asking for money. Maybe once a month someone would run a free tool and blindly send snippets of the output promising the rest in exchange for payment. Or emailing the CFO and the General Counsel after being politely reminded to come back with high quality information, and then ignored until they do.
Your report on the other hand was high quality. I read all the reports that came my way, and good ones were fast tracked for fixes. I'd fix or mitigate them immediately if I had a way to do so without stopping business, and I'd go to the CISO, CTO, and the corresponding engineering manager if it mattered enough for immediate response.
I’ve found Claude in particular to be very good at this sort of thing. As for whether it’s a good thing, I’d say it’s a net positive - your own reporting of this probably saved a bigger issue!
We wrote up the why/what happened on our blog twice… the second based on the LiteLLM issue:
https://grith.ai/blog/litellm-compromised-trivy-attack-chain
I like the presentation <3.
(also beautifully presented!)
The client side tooling needs work, but that's a major effort in and of itself.
PyPI doesn't block package uploads awaiting security scanning - that would be a bad idea for a number of reasons, most notably (in my opinion) that it would be making promises that PyPI couldn't keep and lull people into a false sense of security.
If pypi charges money, python libraries will suddenly have a lot of "you can 'uv add git+https://github.com/project/library'" instead of 'uv add library'.
I also don't think it would stop this attack, where a token was stolen.
If someone's generating pypi package releases from CI, they're going to register a credit card on their account, make it so CI can automatically charge it, and when the CI token is stolen it can push an update on the real package owner's dime, not the attackers, so it's not a deterrent.
Also, the iOS app store is an okay counter example. It charges $100/year for a developer account, but still has its share of malware (certainly more than the totally free debian software repository).
PyPI has paid organization accounts now which are beginning to form a meaningful revenue stream: https://docs.pypi.org/organization-accounts/pricing-and-paym...
Plus a small fee wouldn't deter malware authors, who would likely have easy access to stolen credit cards - which would expose PyPI to the chargebacks and fraudulent transactions world as well!
(software supply chain security is a component of my work)
I agree that's a bad idea to do so since security scanning is inherently a cat and mouse game.
Let's hypothetically say pypi did block upload on passing a security scan. The attacker now simply creates their own pypi test package ahead of time, uploads sample malicious payloads with additional layers of obfuscation until one passes the scan, and then uses that payload in the real attack.
Pypi would also probably open source any security scanning code it adds as part of upload (as it should), so the attacker could even just do it locally.
Maybe the author correctly praises the research capabilities of Claude for some issues. Selecting an Iranian school as a target would be a counterexample.
But the generative parts augmented by claws are a huge and unconditional net negative.
> The litellm_init.pth IS in the official package manifest — the RECORD file lists it with a sha256 hash. This means it was shipped as part of the litellm==1.82.8 wheel on PyPI, not injected locally.
> The infection chain:
> Cursor → futuresearch-mcp-legacy (v0.6.0) → litellm (v1.82.8) → litellm_init.pth
This is the scariest part for me.
I just finished teaching an advanced data science course for one of my clients. I found my self constantly twitching everytime I said "when I write code..." I'm barely writing code at all these days. But I created $100k worth of code just yesterday recreating a poorly maintained (and poor ux) library. Tested and uploaded to pypi in 90 minutes.
A lot of the conversation in my course was directed to leveraged AI (and discussions of existential dread of AI replacement).
This article is a wonderful example of an expert leveraging AI to do normal work 100x faster.
How, exactly, are you calculating the worth of your code? Did you manage to sell in the same day? Why is it "worth $100k"?
If it took 90 minutes + a Claude Code subscription then the most anyone else is going to be willing to pay for the same code is... ~90 minutes of wages + a Claude Code subscription.
Ofc the person earning those wages will be more skilled than most, but unless those skills are incredibly rare & unique, it's unlikely 90 minutes of their time will be worth $100k.
And ofc, the market value of this code could be higher, even much higher, the the cost to produce it, but for this to be the case, there needs to be some sort of moat, some sort of reason another similarly skilled person cannot just use Claude to whip up something similar in their 90 minutes.
Don't use bogus $ from sloccount. Just say I created a 10k line project.
Thank you for your service, this brings so much context into view, it's great.
[1]: https://en.wikipedia.org/wiki/XZ_Utils_backdoor
> While xz is commonly present in most Linux distributions, at the time of discovery the backdoored version had not yet been widely deployed to production systems, but was present in development versions of major distributions.
Ie if you weren’t running dev distros in prod, you probably weren’t exposed.
Honestly a lot of packaging is coming back around to “maybe we shouldn’t immediately use newly released stuff” by delaying their use of new versions. It starts to look an awful lot like apt/yum/dnf/etc.
I would wager in the near future we’ll have another revelation that having 10,000 dependencies is a bad thing because of supply chain attacks.
> I would wager in the near future we’ll have another revelation that having 10,000 dependencies is a bad thing because of supply chain attacks.
Yes, but this also has nothing to do with native vs. non-native.
And not changing often is a feature, yes.
(I don't know what a "sane" distro is; empirically lots of distros are bleeding-edge, so we need to think about these things regardless of value judgements.)
But the data remains: no supply chain attacks on libc yet, so even if it COULD happen, this HAS and that merely COULD.
Do you think supply chain attacks will just get worse? I'm thinking that defensive measures will get better rapidly (especially after this hack)
I think the attacks will get worse and more frequent -- ML tools enable doing it easily among people who were previously not competent enough to pull it off but now can. There is no stomach for the proper defensive measures among the community for either python or javascript. Why am i so sure? This is not the first, second, third, or fourth time this has happened. Nothing changed.