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ReDoS based DoS vulnerability in Active Support's underscoreGHSA-j6gc-792m-qgm2

Fix: rails/rails@2164d4f

GHSA-j6gc-792m-qgm2 is a Uncontrolled Resource Consumption vulnerability in activesupport. A fix is available for activesupport — see the affected versions and patch details below.

Also known asCVE-2023-22796
Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-j6gc-792m-qgm2.

EPSS Exploitation Probability

via FIRST.org ↗
1.7%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs78th percentile — riskier than 78% of all scored CVEsHighest risk
0.98%1.39%1.80%2.21%1.5%1.7%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

2 pkgs affected
💎activesupport💎activesupport

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.

Description

There is a possible regular expression based DoS vulnerability in Active Support. This vulnerability has been assigned the CVE identifier CVE-2023-22796.

Versions Affected: All Not affected: None Fixed Versions: 5.2.8.15 (Rails LTS, which is a paid service and not part of the rubygem), 6.1.7.1, 7.0.4.1 Impact

A specially crafted string passed to the underscore method can cause the regular expression engine to enter a state of catastrophic backtracking. This can cause the process to use large amounts of CPU and memory, leading to a possible DoS vulnerability.

This affects String#underscore, ActiveSupport::Inflector.underscore, String#titleize, and any other methods using these.

All users running an affected release should either upgrade or use one of the workarounds immediately. Releases

The FIXED releases are available at the normal locations. Workarounds

There are no feasible workarounds for this issue.

Users on Ruby 3.2.0 or greater may be able to reduce the impact by configuring Regexp.timeout. Patches

To aid users who aren’t able to upgrade immediately we have provided patches for the two supported release series. They are in git-am format and consist of a single changeset.

6-1-Avoid-regex-backtracking-in-Inflector.underscore.patch - Patch for 6.1 series
7-0-Avoid-regex-backtracking-in-Inflector.underscore.patch - Patch for 7.0 series

Please note that only the 7.0.Z and 6.1.Z series are supported at present, and 6.0.Z for severe vulnerabilities. Users of earlier unsupported releases are advised to upgrade as soon as possible as we cannot guarantee the continued availability of security fixes for unsupported releases.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
💎RubyGemsactivesupportall versions6.1.7.1bundle update activesupport --conservative
💎RubyGemsactivesupport≥ 7.0.0&&< 7.0.4.17.0.4.1bundle update activesupport --conservative

Affected Products

1 product · 2 configurations
Application
activesupportactivesupport_project
≥ 7.0.0 && < 7.0.4.1
range

Detection & mitigation playbook

Open-source dependency
  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for activesupport, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update activesupport to 6.1.7.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-j6gc-792m-qgm2 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate
ProductFixed inAdvisory
Red Hat Satellite 6.14 for RHEL 8rubygem-activesupport-0:6.1.7.3-1.el8satRHSA-2023:6818
RHOL-5.7-RHEL-8openshift-logging/fluentd-rhel8:v1.14.6-152RHSA-2023:4341

Frequently Asked Questions

There is a possible regular expression based DoS vulnerability in Active Support. This vulnerability has been assigned the CVE identifier CVE-2023-22796. Versions Affected: All Not affected: None Fixed Versions: 5.2.8.15 (Rails LTS, which is a paid service and not part of the rubygem), 6.1.7.1, 7.0.4.1 Impact A specially crafted string passed to the underscore method can cause the regular expression engine to enter a state of catastrophic backtracking. This can cause the process to use large amounts of CPU and memory, leading to a possible DoS vulnerability. This affects String#underscore,
O3 Security · Impact-Aware SCA

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ReDoS based DoS vulnerability in Active Support's…