- Severity: MEDIUM
- CVE: CVE-2026-126072
- Ecosystems: rubygems, rubygems
- Packages: actionpack, actionpack
### Impact
`ActionController::Live::Buffer#close` pushes its end-of-stream marker onto the response’s bounded queue while it holds the buffer’s monitor. When the client has stopped reading and the queue is full, the push blocks, and `Buffer#abort`, which runs when the client disconnects or a write times out, waits indefinitely for the same monitor. Each such response could permanently hold a web server thread and its `ActionController::Live` thread, possibly resulting in a DoS vulnerability through thread exhaustion.
Applications that stream responses with `ActionController::Live`, including `send_stream`, are affected. Applications that serve large files through Active Storage proxy mode are exposed to unauthenticated clients.
### Releases
The fixed releases are available at the normal locations.
Patches for those who cannot upgrade at once:
– 8.1: https://github.com/rails/rails/commit/ccbfc09690fef05fdd2a9969c917a71b92cc98fc.patch
– 8.0: https://github.com/rails/rails/commit/27ad18ed5900dee28ba20e9c6fc718ff751fa215.patch
### Credit
This issue was found by the Anthropic OSS Scanner (ANT-2026-LDFW5N2T).
Source: GitHub Security Advisories · 2026-11-12