Codex-Found Node.js Flaw Gets a PoC Exploit

A memory-corruption bug that OpenAI's Codex Security team found in the Brotli decoder bundled with Node.js now has a public proof-of-concept exploit. Node.js patched the flaw, CVE-2026-111497, in security releases on Oct. 21, and within a day Imperva's red team showed code execution on an official Node.js 24.22.0 build, according to reporting by The Hacker News.

Key takeaways

• Node.js 22.23.4, 24.22.1 and 26.12.1 fix CVE-2026-111497, a Brotli decoder out-of-bounds write that the project says can lead to remote code execution.
• Imperva ran attacker code on the official Node.js 24.22.0 Linux arm64 image through fetch() and Express 5 body parsers, though not on every attempt.
• No exploitation in the wild had been reported as of Oct. 23, but Node.js 20.x and older will not be patched, and Bun was still missing the upstream fix in an open issue.

What the Node.js Brotli bug does

The Node.js advisory says an invalid block switch in a Brotli stream "was reported as a temporary need for more input instead of a permanent format error." The streaming decoder then kept appending bytes to an eight-byte internal buffer.

Any attacker who can feed Brotli data to an application that decompresses it with node:zlib "can corrupt process memory, which can lead to a crash, disclosure of process memory, or remote code execution," the advisory says. Node.js rates the issue High. Google, acting as the CVE numbering authority, scored it 9.2 under CVSS 4.0, according to security firms Cycode and HeroDevs.

The advisory credits "OpenAI Codex Security - Khai Tran and Sylvie Mayer" with the report, and Node.js maintainers mcollina and aduh95 with the fix. It was one of 10 CVEs in the release, four of them rated High.

From patch to Node2Shell exploit

The first public proof of concept, posted Oct. 22, reached code execution only on a deliberately weakened test build, The Hacker News reported. On a standard build, its author got a crash and a limited memory read.

Imperva's red team, which named the attack Node2Shell, went further the same day. It reproduced code execution on Express 5.0.0–5.3.0 with body-parser 2.0.0–2.3.0, through both incoming request bodies and Brotli-compressed responses read by fetch(). A plain Node.js HTTP server does not decode Brotli just by receiving it. Imperva did not test other architectures or the 22.x and 26.x lines, and Node.js 24.22.1 rejected the same input.

Who still needs to patch

Google's Brotli project shipped v1.2.1, v1.1.1 and v1.0.10 on Oct. 21 listing the CVE. Runtimes that vendor the library need their own update. A GitHub issue opened Oct. 21 says "Every Bun release is affected," with a backport pull request waiting on blocked CI.

Node.js 20.x and earlier are end-of-life and will not receive the fix. HeroDevs, which sells extended support for old versions, says it found the vulnerable decoder in 20.20.2 and 18.20.8. Qualys advises teams to rebuild container images and single-executable apps and restart long-running services after upgrading.

Why AI-found bugs matter here

The case shows how fast an AI-found bug now goes from private report to working exploit once the fix is public. The same tools help both sides, as we saw when attackers ran agents that rebuilt their malware until scanners stopped catching it.

What's next

Imperva and Vercel have added firewall rules, but Vercel's rules cover only inbound requests, not Brotli responses an app fetches from other servers. Imperva said "only the update removes the flaw." The CVE was not in CISA's Known Exploited Vulnerabilities catalog as of Oct. 23.

FAQ

Which Node.js versions fix CVE-2026-111497?

Node.js 22.23.4, 24.22.1 and 26.12.1, or any later release in those lines. The advisory lists no workaround.

Is Node2Shell being exploited in the wild?

None had been reported as of Oct. 23. Public proof-of-concept code exists, and Imperva's code execution was not reliable on every attempt.

Am I exposed if I run an older Node.js?

Node.js 20.x and earlier are end-of-life and get no fix. Moving to a supported line is the only upstream remedy.

References

• Node.js — Wednesday, October 21, 2026 Security Releases — Node.js (Oct. 21, 2026)
• Researchers Demonstrate Node2Shell RCE Exploit on Node.js Build Using Crafted Brotli Data — The Hacker News (Oct. 23, 2026)
• Releases · google/brotli — GitHub
• Brotli decoder is missing the CVE-2026-111497 fix (google/brotli@0ed4268a) — GitHub, oven-sh/bun (Oct. 21, 2026)
• Node.js Patches Brotli Remote Code Execution Flaw: Find Vulnerable Runtimes Before Attackers Do — Qualys (Oct. 23, 2026)
• node2shell (CVE-2026-111497): What to Patch in Node.js — Cycode (Oct. 23, 2026)
• CVE-2026-111497 (Node2Shell): Node.js Brotli RCE Fix — HeroDevs (Oct. 23, 2026)