Mythos Finds 23-Year-Old NFS Root and Chains Firefox Bugs

Indie Hacker News2026-05-10go watch the original →

the gist

Anthropic's Mythos AI, via a bash for-loop on Linux kernel files, uncovered a remote root in NFS since 2003; it scores 83.1% on CyberGym vs. prior 66.6%, chains 4 Firefox bugs for shell, but access is restricted to 12 partners at $25/M tokens.

The Breakthrough

Anthropic's Mythos model discovered a remote root exploit in the Linux kernel's NFS driver that had existed since 2003, using a simple bash for-loop script iterating through source files.

What Actually Worked

Mythos identified a signed integer overflow in OpenBSD's TCP stack, exploitable via crafted SACK blocks, which had crashed servers since 1998.
Mythos found a heap corruption bug in FFmpeg's H.264 slice numbering, missed by automated fuzzing after 5 million attempts and dormant for 16 years.
Mythos autonomously exploited a full remote code execution vulnerability in FreeBSD's network file-share daemon, assigned CVE-2026-4747.
Mythos chained four bugs in Firefox version 147: JIT type confusion, predictable garbage collector behavior, renderer sandbox escape, and kernel privilege escalation; it wrote a JIT heap spray and obtained a shell without human guidance.

Before / After

Mythos achieved 83.1% on the CyberGym vulnerability reproduction benchmark, compared to Opus's 66.6%. On Firefox, the older model required hundreds of attempts for two exploits, while Mythos produced 181. On Google's open-source fuzz suite, Mythos crashed 595 programs and achieved full control-flow hijack on 10 fully patched targets; Opus achieved zero in that category. 99% of bugs filed by Mythos remain unpatched.

Context

Anthropic researcher ran a bash for-loop script asking Claude Code to scan Linux kernel files for bugs, revealing the NFS exploit. Anthropic then restricted Mythos access via Project Glasswing to 12 partners including Apple, Google, Microsoft, JPMorgan, and the Linux Foundation, charging $25 per million input tokens (5x regular Claude). Open-source maintainers face incoming reports they cannot triage affordably, inverting defender-attacker economics as vulnerability-to-exploit windows shrink from months to minutes.

Notable Quotes

Sam Altman: "We have built a bomb. We are about to drop it on your head, we will sell you a bomb shelter for one hundred million dollars."
Greg Kroah-Hartman: "The slop ended. The reports are real now."
Daniel Stenberg (Curl): "His triage queue went from a slop tsunami to a real bug tsunami."
Bruce Schneier: "A sea change. It just happened sooner than anyone is ready for."
CrowdStrike's Elia Zaitsev: "The window between vulnerability and exploit just collapsed."

Content References

Apache Software Foundation received a $1.5M grant and Alpha-Omega a $2.5M top-up for Mythos access.