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VulnerabilityPublished

CVE-2026-126076: Action Pack · Possible restoration of destroyed sessions in Action Dispatch CacheStore

Affects actionpackSource GCVE Database

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Authoritative record:CVE-2026-126076· Medium 4.2

Not known to be exploited · CVSS 4.2 Medium : upgrade to 8.1.4.1 when convenient.

Data as of 10 Nov 2026, 22:34 UTC

CVSS 3.1 base score
4.2Medium
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 3.14.2
Patch
Available – fixed in 8.1.4.1, 8.0.5.2
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N

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 10 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 `ActionDispatch::Session::CacheStore` writes a session back to the cache at the end of each request that loaded it, without checking that the session's cache entry still exists. When a concurrent request destroys the session, through `reset_session` on logout or by deleting its cache entry on the server, a request that loaded the session earlier and finishes later restores it under its original session ID. Logout and server-side revocation could therefore fail to end a session, and an attacker who holds a stolen session cookie could keep that session valid across the victim's logout. Applications that use `config.session_store :cache_store` are affected, with any cache backend. `ActionDispatch::Session::CookieStore` is not affected, nor is `ActionDispatch::Session::MemCacheStore` with Dalli 4.0.0 or later, whose session store does not write back a session that was deleted. ### Details The fixed releases record which session a request loaded and skip the write when that session's cache entry no longer exists. Changes that such a request makes to the destroyed session are discarded, and Rack logs a warning that the session could not be saved. Each request that writes back a session it loaded makes one additional cache read. ### 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/d479192cf88a8b30a335a8bc25188a2d8e0f8d9f.patch - 8.0: https://github.com/rails/rails/commit/5bb5ec66ed8faaf590ffe1222d7a5eb6e9d050f5.patch ### Credit Found by the team during internal code review.

References

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