PT-2026-29819 · Rack · Rack

Oblivionsage · Published 2026-04-02 · Updated 2026-04-02 · CVE-2026-34831

NVD

CVSS v3.1

4.8

Medium

AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

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.

Fix

Weakness Enumeration

CWE-130

CWE-135

Related Identifiers

CVE-2026-34831

Affected Products

Rack

References · 2

• https://nvd.nist.gov/vuln/detail/CVE-2026-34831 · Security Note
• https://github.com/rack/rack/security/advisories/GHSA-q2ww-5357-x388 · Note