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VulnerabilityPublished

CVE-2026-126073: rails · Interpretation Conflict

Affects railsSource CVE Database V5

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Not known to be exploited · CVSS 4.8 Medium : upgrade to 8.1.4.1 or 8.0.5.2 when convenient.

Data as of 10 Nov 2026, 21:07 UTC

CVSS 3.1 base score
4.8Medium
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 3.14.8
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:L/A:L

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 rails to 8.1.4.1 or 8.0.5.2.

Affected software

ProductAffectedFixed in
railsrailsAffected
  • >=8.1 <8.1.4.1
Fixed in
  • 8.1.4.1
railsrailsAffected
  • <8.0.5.2
Fixed in
  • 8.0.5.2

AI-suggested

This vulnerability is fixed in Rails versions 8.1.4.1 and 8.0.5.2. Users should upgrade to these or later versions to remediate the issue. No additional mitigation is required if the application is updated. If upgrading is not immediately possible, consider disabling public caching of negotiated responses or using caches that do not honor the Vary header until a patch is applied.

Description

CVE-2026-126073 is a medium severity vulnerability in the Rails Action Pack framework affecting versions prior to 8.1.4.1 and 8.0.5.2. The issue involves improper handling of the Vary HTTP header when negotiating response formats based on request headers. This can lead to cache poisoning in shared caches that honor the Vary header, causing clients to receive incorrect content representations until the cache entry expires. The vulnerability is fixed in Rails versions 8.1.4.1 and 8.0.5.2.

References

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