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Anthropic disclosed that its Claude Mythos Preview model autonomously discovered and, in some cases, exploited vulnerabilities across major software targets, including Firefox, OpenBSD, FreeBSD, Linux, FFmpeg, cryptography libraries, and a memory-safe virtual machine monitor. The company said the system produced browser exploit chains involving JIT heap sprays and sandbox escapes, chained Linux kernel flaws into local privilege escalation, and developed a fully autonomous exploit for CVE-2026-4747, a FreeBSD NFS issue that reportedly enables unauthenticated remote root access. Anthropic said most findings remain under coordinated disclosure because fewer than 1% had been patched at the time of publication.
Publicly described examples included a 27-year-old OpenBSD SACK denial-of-service bug that was later addressed in an OpenBSD patch, and a 16-year-old FFmpeg H.264 out-of-bounds write. Anthropic also said it partnered with Mozilla to improve Firefox security, underscoring that modern AI systems are now capable of meaningful autonomous vulnerability research against widely deployed platforms. To limit immediate misuse, the company withheld most technical details and published SHA-3 commitments for future disclosure while urging defenders to accelerate AI-assisted bug hunting, patching, disclosure coordination, and incident-response automation.
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4 events from the most recent confirmed update back to the earliest known activity.
Anthropic reported that Claude Mythos Preview had autonomously discovered and in some cases exploited zero-day and N-day vulnerabilities across software including OpenBSD, FreeBSD, Linux, FFmpeg, browsers, and cryptography libraries. It publicly highlighted examples including an OpenBSD SACK denial-of-service bug, an FFmpeg H.264 out-of-bounds write, and a FreeBSD NFS remote root issue tracked as CVE-2026-4747, while withholding most details under coordinated disclosure.
OpenBSD published patch 025 for version 7.8 addressing a SACK-related issue, as indicated by the patch signature file in the OpenBSD patches repository. This aligns with later reporting that a long-standing OpenBSD SACK denial-of-service bug had been found.
The paper "AddressSanitizer: A Fast Address Sanity Checker" was presented at the 2012 USENIX Annual Technical Conference in Boston, Massachusetts. The conference entry identifies the authors as Konstantin Serebryany, Derek Bruening, Alexander Potapenko, and Dmitriy Vyukov.
Anthropic published a post about partnering with Mozilla to improve Firefox's security. The reference indicates this announcement was published on 2026-03-06, but the synopsis provides no additional dated event details.
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Anthropic reported that **Claude Opus 4.6** identified **22 security vulnerabilities in Mozilla Firefox** during a **two-week** collaboration with Mozilla, with **14** categorized as **high severity**. The work began in Firefox’s **JavaScript engine** and expanded across the broader codebase, demonstrating that an AI model can rapidly surface memory-safety and other complex issues in a mature, heavily scrutinized open-source project; one example cited was a **use-after-free** class bug discovered early in the effort. Mozilla validated the findings and shipped fixes, with most issues addressed in **Firefox 148** (and some remediations deferred to a subsequent release, per reporting). Separate reporting discussed market and product implications of Anthropic’s *Claude Code Security* feature—an AI-assisted code-scanning capability that suggests patches and is positioned as an alternative to traditional rules-based static analysis—along with investor reactions affecting major security vendors. While related to AI-driven secure development, that coverage does not describe the Firefox vulnerability-discovery engagement itself and is better treated as adjacent industry context rather than part of the same specific event.
Jun 29, 2026
Anthropic unveiled **Claude Mythos Preview**, an unreleased AI model it says can autonomously discover and exploit severe software vulnerabilities across major operating systems, browsers, open-source projects, and some closed-source targets. The company said the model uncovered thousands of high-severity flaws, including long-lived bugs in **OpenBSD**, **FFmpeg**, Linux kernel privilege-escalation chains, and **`CVE-2026-4747`**, a FreeBSD NFS remote code execution flaw that could enable unauthenticated root access. Anthropic withheld broad release, citing offensive cyber risk, and instead launched **Project Glasswing**, a gated program for roughly 40 to 50 partners such as AWS, Apple, Cisco, Cloudflare, Google, JPMorgan Chase, Microsoft, Mozilla, NVIDIA, and Palo Alto Networks to validate findings, patch affected software, and study defensive uses. Independent and industry assessments broadly agreed Mythos marks a significant advance in AI-enabled cyber capability, though several researchers questioned how much of Anthropic’s headline claims can yet be verified through public CVEs and warned that similar results may be reproducible with cheaper or open models plus strong tooling. The UK AI Security Institute found Mythos achieved a **73%** success rate on expert capture-the-flag tasks and completed a full 32-step simulated enterprise attack in 3 of 10 runs, while Anthropic later reported coordinated disclosure activity spanning **1,596 vulnerabilities across 281 open-source projects** and partners identifying more than **10,000** high- or critical-severity candidates. Governments, financial regulators, and CISO groups in the US, UK, Europe, Canada, and Japan responded with briefings and warnings that AI is compressing the gap between vulnerability discovery and weaponization, leaving remediation, patch governance, and defensive automation as the main bottlenecks.
Jun 29, 2026
Mozilla said **Firefox 150** shipped with fixes for **271 security vulnerabilities** identified during an early evaluation of Anthropic’s restricted **Claude Mythos Preview** model, a sharp increase from the **22 bugs** previously found with Anthropic’s Opus 4.6 in Firefox 148. Mozilla CTO Bobby Holley said the findings created a major engineering burden and forced reprioritization, but argued the work was necessary because AI-assisted vulnerability discovery is rapidly improving and can now reason about source code at a level Mozilla compared to elite human researchers. Mozilla said the model did not uncover wholly new classes of flaws beyond human capability, but it found known types of bugs at much greater speed and scale, including issues traditional fuzzing might miss.
Jun 29, 2026