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-YYYY-XXXX.

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!