Summary
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!
Impact
A regular expression with worst-case exponential or polynomial matching time is applied to untrusted input, causing excessive CPU use. Typical impact: denial of service when input is crafted to trigger backtracking.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
rack to 3.0.9.1 or later; rack to 2.2.8.1 or later; rack to 2.1.4.4 or later; rack to 2.0.9.4 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2024-26146? CVE-2024-26146 is a low-severity inefficient regular expression (ReDoS) vulnerability in rack (rubygems), affecting versions >= 3.0.0, < 3.0.9.1. It is fixed in 3.0.9.1, 2.2.8.1, 2.1.4.4, 2.0.9.4. A regular expression with worst-case exponential or polynomial matching time is applied to untrusted input, causing excessive CPU use.
- Which versions of rack are affected by CVE-2024-26146? rack (rubygems) versions >= 3.0.0, < 3.0.9.1 is affected.
- Is there a fix for CVE-2024-26146? Yes. CVE-2024-26146 is fixed in 3.0.9.1, 2.2.8.1, 2.1.4.4, 2.0.9.4. Upgrade to this version or later.
- Is CVE-2024-26146 exploitable, and should I be worried? Whether CVE-2024-26146 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2024-26146 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2024-26146?
- Upgrade
rackto 3.0.9.1 or later - Upgrade
rackto 2.2.8.1 or later - Upgrade
rackto 2.1.4.4 or later - Upgrade
rackto 2.0.9.4 or later
- Upgrade