Opus 4.6 uncovers 500 zero-day flaws in open-source code

https://www.axios.com/2026/02/05/anthropic-claude-opus-46-software-hunting

Exclusive: Anthropic's new model is a pro at finding security flaws

The AI company sees the model's advancements as a major win for cyber defenders in the race against adversarial AI.

Axios

The system card unfortunately only refers to this [0] blog post and doesn't go into any more detail. In the blog post Anthropic researchers claim: "So far, we've found and validated more than 500 high-severity vulnerabilities".

The three examples given include two Buffer Overflows which could very well be cherrypicked. It's hard to evaluate if these vulns are actually "hard to find". I'd be interested to see the full list of CVEs and CVSS ratings to actually get an idea how good these findings are.

Given the bogus claims [1] around GenAI and security, we should be very skeptical around these news.

[0] https://red.anthropic.com/2026/zero-days/

[1] https://doublepulsar.com/cyberslop-meet-the-new-threat-actor...

0-Days \ red.anthropic.com

I know some of the people involved here, and the general chatter around LLM-guided vulnerability discovery, and I am not at all skeptical about this.
[flagged]
Nobody is right about everything, but tptacek's takes on software security are a good place to start.

I'm interested in whether there's a well-known vulnerability researcher/exploit developer beating the drum that LLMs are overblown for this application. All I see is the opposite thing. A year or so ago I arrived at the conclusion that if I was going to stay in software security, I was going to have to bring myself up to speed with LLMs. At the time I thought that was a distinctive insight, but, no, if anything, I was 6-9 months behind everybody else in my field about it.

There's a lot of vuln researchers out there. Someone's gotta be making the case against. Where are they?

From what I can see, vulnerability research combines many of the attributes that make problems especially amenable to LLM loop solutions: huge corpus of operationalizable prior art, heavily pattern dependent, simple closed loops, forward progress with dumb stimulus/response tooling, lots of search problems.

Of course it works. Why would anybody think otherwise?

You can tell you're in trouble on this thread when everybody starts bringing up the curl bug bounty. I don't know if this is surprising news for people who don't keep up with vuln research, but Daniel Stenberg's curl bug bounty has never been where all the action has been at in vuln research. What, a public bug bounty attracted an overwhelming amount of slop? Quelle surprise! Bug bounties have attracted slop for so long before mainstream LLMs existed they might well have been the inspiration for slop itself.

Also, a very useful component of a mental model about vulnerability research that a lot of people seem to lack (not just about AI, but in all sorts of other settings): money buys vulnerability research outcomes. Anthropic has eighteen squijillion dollars. Obviously, they have serious vuln researchers. Vuln research outcomes are in the model cards for OpenAI and Anthropic.

It does if the person making the statement has a track record, proven expertise on the topic - and in this case… it actually may mean something to other people

Yes, as we all know that unsourced unsubstantiated statements are the best way to verify claims regarding engineering practices. Especially when said person has a financial stake in the outcomes of said claims.

No conflict of interest here at all!

I have zero financial stake in Anthropic and more broadly my career is more threatened by LLM-assisted vulnerability research (something I do not personally do serious work on) than it is aided by it, but I understand that the first principal component of casual skepticism on HN is "must be a conflict of interest".
You still haven't answered why I should care that you, a stranger on the internet, believes some unsubstantiated hearsay?

Take a look at https://news.ycombinator.com/leaders

The user you're suspicious of is pretty well-known in this community.

Leaders | Hacker News

How is this whole comment chain not a textbook case of "argument from authority"? I claim A, a guys says. Why would I trust you somebody else responds. Well he's pretty well known on the internet forum we're all on, the third guy says, adding nothing to the conversation.

it is literally just "authority said so".

and its ridiculous that someone's comment got flagged for not worshiping at the alter of tptacek. they weren't even particularly rude about it.

i guarantee if i said what tptacek said, and someone replied with exactly what malfist said, they would not have been flagged. i probably would have been downvoted.

why appeal to authority is totally cool as long as tptacek is the authority is way fucking beyond me. one of those HN quirks. HN people fucking love tptacek and take his word as gospel.

I am very lovable.
:| iyho?
I don't think it's debatable.
Do you have a letter of recommendation?
Very several.
Contra Ptacek's Terrible Article On AI — Ludicity

Here's a fun exercise: go email the author of that blog (he's very nice) and ask how much of it he still stands by.