CVE-2024-26146 is a medium-severity (CVSS 5.3) CWE-1333 vulnerability in rack. A fix is available for rack — see the affected versions and patch details below.
Possible Denial of Service Vulnerability in Rack Header Parsing
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 CVE-2024-26146.
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-2024-26146 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 377,636 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
rack💎rack💎rack💎rackReal-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 Denial of Service Vulnerability in Rack Header Parsing
There is a possible denial of service vulnerability in the header parsing routines in Rack. This vulnerability has been assigned the CVE identifier CVE-2024-26146.
Versions Affected: All. Not affected: None Fixed Versions: 2.0.9.4, 2.1.4.4, 2.2.8.1, 3.0.9.1
Impact
Carefully crafted headers can cause header parsing in Rack to take longer than expected resulting in a possible denial of service issue. Accept and Forwarded headers are impacted.
Ruby 3.2 has mitigations for this problem, so Rack 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.
- 2-0-header-redos.patch - Patch for 2.0 series
- 2-1-header-redos.patch - Patch for 2.1 series
- 2-2-header-redos.patch - Patch for 2.2 series
- 3-0-header-redos.patch - Patch for 3.0 series
Credits
Thanks to svalkanov for reporting this and providing patches!
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | rack | ≥ 3.0.0&&< 3.0.9.1 | 3.0.9.1bundle update rack --conservative |
| 💎RubyGems | rack | ≥ 2.2.0&&< 2.2.8.1 | 2.2.8.1bundle update rack --conservative |
| 💎RubyGems | rack | ≥ 2.1.0&&< 2.1.4.4 | 2.1.4.4bundle update rack --conservative |
| 💎RubyGems | rack | all versions | 2.0.9.4bundle update rack --conservative |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rack, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update rack to 3.0.9.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-26146 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-2024-26146 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2024-26146. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 8 | pcs-0:0.10.18-2.el8_10 | RHSA-2024:2953 |
| Red Hat Enterprise Linux 8.2 Telecommunications Update Service | pcs-0:0.10.4-6.el8_2.5 | RHSA-2024:2007 |
| Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support | pcs-0:0.10.8-1.el8_4.5 | RHSA-2024:2584 |
| Red Hat Enterprise Linux 8.6 Extended Update Support | pcs-0:0.10.12-6.el8_6.5 | RHSA-2024:3431 |
| Red Hat Enterprise Linux 8.8 Extended Update Support | pcs-0:0.10.15-4.el8_8.2 | RHSA-2024:2581 |
| Red Hat Enterprise Linux 9 | pcs-0:0.11.7-2.el9_4 | RHSA-2024:2113 |
| Red Hat Enterprise Linux 9.0 Extended Update Support | pcs-0:0.11.1-10.el9_0.5 | RHSA-2024:1841 |
| Red Hat Enterprise Linux 9.2 Extended Update Support | pcs-0:0.11.4-7.el9_2.1 | RHSA-2024:1846 |
Frequently Asked Questions
Is CVE-2024-26146 in your dependencies?
O3 Security finds CVE-2024-26146 across RubyGems dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.