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No exploitation reportedFix availableAwaiting NVD analysis

CVE-2026-126080

Active Support: Possible DoS vulnerability in Active Support safe_constantize

No exploitation reported by the sources we read.

  • Published2026-11-10
  • Fixed in8.1.4.1 · 8.0.5.2
  • WeaknessCWE-74

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Active Support is a collection of utility classes and standard library extensions used by Rails and other Ruby projects. Prior to 8.1.4.1 and 8.0.5.2, when constant lookup raises LoadError, ActiveSupport::Inflector#safe_constantize (and String#safe_constantize) builds a regular expression from the requested constant name without escaping it, so a caller that passes untrusted input lets the attacker choose the source of a pattern that the application compiles. Crafted patterns can trigger defects in Ruby's regular expression compiler, possibly leading to a crash of the server process, and repeated requests could keep the application unavailable. Action Cable passes the channel value of each subscribe command to safe_constantize before any channel lookup, so an unauthenticated client can reach this code when the application mounts Action Cable and accepts connections from untrusted clients without an added authentication check. This issue is fixed in versions 8.1.4.1 and 8.0.5.2.

Timeline

dates in UTC
  1. 2026-11-1021:04CVE publishedCNA

Versions per branch

OSV
activesupport
BranchAffectedFixed in
8.1≥ 8.1.0.beta1, < 8.1.4.18.1.4.1
8.0< 8.0.5.28.0.5.2

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA1 product

As GitHub_M, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • rails
    Affected
    • = >= 8.1, < 8.1.4.1no fix stated
    • = < 8.0.5.2no fix stated

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-11-10

Fix

  1. Update activesupport to 8.1.4.1 · 8.0.5.2

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Metasploit modules
none listed
Metasploit Framework

Sources

  • CNACVSS 3.17.52026-11-10
  • CNAweakness (CWE)CWE-742026-11-10
  • NVDweakness (CWE)CWE-74read 2026-11-10
  • OSVaffected packages—
  • GitHub AdvisoriesadvisoryHIGH2026-11-10

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
2026-11-10
Last Modified
2026-11-10
NVD status
Received
GitHub Advisory
GHSA-8474-xrp6-wh69

Frequently asked questions

What is CVE-2026-126080?

Active Support is a collection of utility classes and standard library extensions used by Rails and other Ruby projects. Prior to 8.1.4.1 and 8.0.5.2, when constant lookup raises LoadError, ActiveSupport::Inflector#safe_constantize (and String#safe_constantize) builds a regular expression from the requested constant name without escaping it, so a caller that passes untrusted input lets the attacker choose the source of a pattern that the application compiles. Crafted patterns can trigger defects in Ruby's regular expression compiler, possibly leading to a crash of the server process, and repeated requests could keep the application unavailable. Action Cable passes the channel value of each subscribe command to safe_constantize before any channel lookup, so an unauthenticated client can reach this code when the application mounts Action Cable and accepts connections from untrusted clients without an added authentication check. This issue is fixed in versions 8.1.4.1 and 8.0.5.2.

Is CVE-2026-126080 actively exploited?

Active exploitation of CVE-2026-126080 has not been confirmed.

What is the CVSS score for CVE-2026-126080?

CVE-2026-126080 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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