CVE-2024-26142 is a high-severity (CVSS 7.5) CWE-1333 vulnerability in actionpack. A fix is available for actionpack — see the affected versions and patch details below.
Rails possible ReDoS vulnerability in Accept header parsing in Action Dispatch
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2024-26142.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2024-26142 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
actionpackReal-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
Possible ReDoS vulnerability in Accept header parsing in Action Dispatch
There is a possible ReDoS vulnerability in the Accept header parsing routines of Action Dispatch. This vulnerability has been assigned the CVE identifier CVE-2024-26142.
Versions Affected: >= 7.1.0, < 7.1.3.1 Not affected: < 7.1.0 Fixed Versions: 7.1.3.1
Impact
Carefully crafted Accept headers can cause Accept header parsing in Action Dispatch to take an unexpected amount of time, possibly resulting in a DoS vulnerability. All users running an affected release should either upgrade or use one of the workarounds immediately.
Ruby 3.2 has mitigations for this problem, so Rails applications using Ruby 3.2 or newer are unaffected.
Releases
The fixed releases are available at the normal locations.
Workarounds
There are no feasible workarounds for this issue.
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.
- 7-1-accept-redox.patch - Patch for 7.1 series
Credits
Thanks svalkanov for the report and patch!
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | actionpack | ≥ 7.1.0&&< 7.1.3.1 | 7.1.3.1bundle update actionpack --conservative |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for actionpack, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update actionpack to 7.1.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-26142 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2024-26142 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2024-26142. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2024-26142 in your dependencies?
O3 Security finds CVE-2024-26142 across RubyGems dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.