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High, CVSS 7.5amended

Active Support: Possible DoS vulnerability in Active Support safe_constantize

CVE-2026-126080GHSA-8474-xrp6-wh69

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (activesupport 8.1.4.1, 8.0.5.2), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • RubyGems activesupport

    Affected
    >= 8.1.0.beta1, < 8.1.4.1< 8.0.5.2
    Fixed in
    8.0.5.2, 8.1.4.1

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

Impact 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 in the default configuration an unauthenticated client of the Action Cable endpoint can reach this code.

Details The check that decides whether `safe_constantize` returns `nil` or re-raises the `LoadError` now matches the first segment of the constant name against the error message as a literal string, and no longer compiles a regular expression. It…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from osv record GHSA-8474-xrp6-wh69

  2. Revision 1 · created ·

    Published from ghsa record GHSA-8474-xrp6-wh69

Agent brief

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# Patch Next advisory brief: CVE-2026-126080

Advisory: Active Support: Possible DoS vulnerability in Active Support safe_constantize
IDs: CVE-2026-126080, GHSA-8474-xrp6-wh69
Record: https://patchnext.com/advisories/cve-2026-126080 (revision 2, source checked 11 Nov 2026, 07:35 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: activesupport 8.1.4.1, 8.0.5.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems activesupport: affected >= 8.1.0.beta1, < 8.1.4.1; < 8.0.5.2; fixed in 8.0.5.2, 8.1.4.1

## Suggested inspection (read-only)
- RubyGems activesupport: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on activesupport.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-8474-xrp6-wh69 (GitHub-reviewed advisory GHSA-8474-xrp6-wh69 lists affected ranges: RubyGems activesupport >=8.1.0.beta1 =0 <8.0.5.2)
- Verified: https://osv.dev/vulnerability/GHSA-8474-xrp6-wh69 (OSV record GHSA-8474-xrp6-wh69 lists affected ranges: RubyGems activesupport >=8.1.0.beta1 =0 <8.0.5.2 (fixed))

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