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VulnerabilityPublished

CVE-2026-126072: Action Pack · Possible DoS vulnerability in Action Controller Live streaming

Affects actionpackSource GCVE Database

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Authoritative record:CVE-2026-126072· Medium 5.9

Not known to be exploited · CVSS 5.9 Medium : upgrade to 8.1.4.1 when convenient.

Data as of 13 Nov 2026, 00:06 UTC

CVSS 3.1 base score
5.9Medium
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (GitHub_M)CVSS 3.15.9
Patch
Available – fixed in 8.1.4.1, 8.0.5.2
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 10 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 12 Nov 2026.

What to do

Upgrade actionpack to 8.1.4.1; actionpack to 8.0.5.2.

Affected software

ProductAffectedFixed in
RubyGemsactionpackAffected
  • >=8.1.0.beta1 <8.1.4.1
Fixed in
  • 8.1.4.1
RubyGemsactionpackAffected
  • <8.0.5.2
Fixed in
  • 8.0.5.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

### 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).

References

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