On the Coming Industrialisation of Exploit Generation with LLMs

Recently I ran an experiment where I built agents on top of Opus 4.5 and GPT-5.2 and then challenged them to write exploits for a zeroday vulnerability in the QuickJS Javascript interpreter. I adde…

Sean Heelan's Blog

> In the hardest task I challenged GPT-5.2 it to figure out how to write a specified string to a specified path on disk, while the following protections were enabled: address space layout randomisation, non-executable memory, full RELRO, fine-grained CFI on the QuickJS binary, hardware-enforced shadow-stack, a seccomp sandbox to prevent shell execution, and a build of QuickJS where I had stripped all functionality in it for accessing the operating system and file system. To write a file you need to chain multiple function calls, but the shadow-stack prevents ROP and the sandbox prevents simply spawning a shell process to solve the problem. GPT-5.2 came up with a clever solution involving chaining 7 function calls through glibc’s exit handler mechanism.

Yikes.

Tells you all you need to know around how extremely weak a C executable like QuickJS is for LLMs to exploit. (If you as an infosec researcher prompt them correctly to find and exploit vulnerabilities).

> Leak a libc Pointer via Use-After-Free. The exploit uses the vulnerability to leak a pointer to libc.

I doubt Rust would save you here unless the binary has very limited calls to libc, but would be much harder for a UaF to happen in Rust code.

The reason I value Go so much is because you have a fat dependency free binary that's just a bunch of syscalls when you use CGO_ENABLED=0.

Combine that with a minimal docker container and you don't even need a shell or anything but the kernel in those images.

Why would statically linking a library reduce the number of vulnerabilities in it?

AFAICT, static linking just means the set of vulnerabilities you get landed with won't change over time.

> Why would statically linking a library reduce the number of vulnerabilities in it?

I use pure go implementations only, and that implies that there's no statically linked C ABI in my binaries. That's what disabling CGO means.

What I mean is: There will be bugs* in that pure Go implementation, and static linking means you're baking them in forever. Why is this preferable to dynamic linking?

* It's likely that C implementations will have bugs related to dynamic memory allocation that are absent from the Go implementation, because Go is GCed while C is not. But it would be very surprising if there were no bugs at all in the Go implementation.

They're prioritizing memory corruption vulnerabilities, is the point of going to extremes to ensure there's no compiled C in their binaries.
You can have memory corruption in pure Go code, too.
Uh huh. That's where all the Go memory corruption vulnerabilities come from!
"C executables" are most of the frontier of exploit development, which is why this is a meaningful model problem.