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, < Not affected: < 7.1.0 Fixed Versions:


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.


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.

  • 7-1-accept-redox.patch - Patch for 7.1 series


Thanks svalkanov for the report and patch!

7-1-accept-redos.patch (1.9 KB)