| Name | CVE-2026-34831 |
| Description | Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Files#fail sets the Content-Length response header using String#size instead of String#bytesize. When the response body contains multibyte UTF-8 characters, the declared Content-Length is smaller than the number of bytes actually sent on the wire. Because Rack::Files reflects the requested path in 404 responses, an attacker can trigger this mismatch by requesting a non-existent path containing percent-encoded UTF-8 characters. This results in incorrect HTTP response framing and may cause response desynchronization in deployments that rely on the incorrect Content-Length value. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6. |
| Source | CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
| References | DLA-4706-1, DSA-6492-1 |
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|---|---|---|
| ruby-rack (PTS) | bookworm | 2.2.22-0+deb12u1 | vulnerable |
| bookworm (security) | 2.2.22-0+deb12u2 | fixed | |
| trixie | 3.1.20-0+deb13u1 | vulnerable | |
| trixie (security) | 3.1.20-0+deb13u2 | fixed | |
| forky, sid | 3.2.7-1 | fixed |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|---|---|---|---|---|---|
| ruby-rack | source | experimental | 3.2.6-1 | |||
| ruby-rack | source | bullseye | 2.1.4-3+deb11u6 | DLA-4706-1 | ||
| ruby-rack | source | bookworm | 2.2.22-0+deb12u2 | DLA-4706-1 | ||
| ruby-rack | source | trixie | 3.1.20-0+deb13u2 | DSA-6492-1 | ||
| ruby-rack | source | (unstable) | 3.2.6-2 |
https://github.com/rack/rack/security/advisories/GHSA-q2ww-5357-x388
Fixed by: https://github.com/rack/rack/commit/10ecd9a8a02083297f925f0d9255a93ebde4c0da (v3.2.6)
Fixed by: https://github.com/rack/rack/commit/c3645d377f0335a779812bf3f36e238d87d9b4e6 (v3.1.21)
Fixed by: https://github.com/rack/rack/commit/a75847314e8ad847a5b66e7215381c4ed51f6aa7 (v2.2.23)