OpenAI: red-teaming found an unauthenticated RCE in the Brotli compression library
OpenAI @OpenAIX
Why it matters
Primary disclosure of a model-found remote-code-execution bug in a library embedded in Node.js, Bun and Envoy (CVE-2026-111497), 1.2M views.
Summary
Posted Oct 23, 2026 (22:55 UTC). During the containment red-teaming, OpenAI’s agents found an unauthenticated RCE in Brotli. Malicious compressed data can take over unpatched servers or clients. The root cause had been fixed in Brotli’s source in February without being recognised as a security issue, and no release included it. OpenAI disclosed it to Brotli and downstream projects such as Node.js; Brotli cut new releases and published a CVE. Details: patchtheplanet.org/brotli.
Metrics as of 2026-10-24 via api.fxtwitter.com: 1,198,843 views.
Archived text
During this red-teaming exercise, we also found a vulnerability that allows for unauthenticated remote code execution in Brotli, a widely-deployed compression library included in many pieces of software such as Node.js, Bun, and Envoy.
The flaw could let an attacker run their own code on affected systems by sending or replying with malicious compressed data, without any need to create a user account. That is, an unpatched server that accepts compressed input could be taken over by a malicious client, and an unpatched client that accepts compressed input (such as “curl --compressed”) could be taken over by a malicious server.
This root cause issue was actually fixed in the Brotli source code in February, but it wasn’t known at the time that it gave rise to a security vulnerability and there was no more recent release of Brotli. Since Brotli is built into other software, any software which includes this library needs to take the update too, followed by the users of that software. We disclosed the vulnerability to Brotli and other downstream projects such as Node.js, which released or are currently releasing security updates, and Brotli cut new release versions and published a CVE.