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:,,,


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.


The fixed releases are available at the normal locations.


There are no feasible workarounds for this issue.


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


Thanks to svalkanov for reporting this and providing patches!

2-0-header-redos.patch (906 Bytes) 2-1-header-redos.patch (922 Bytes) 2-2-header-redos.patch (890 Bytes) 3-0-header-redos.patch (1.5 KB)

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