CVEvulnerability
CVE-2026-34831
6.5 MEDIUM
Official page ↗
- Status
- Analyzed
- Published
- 2026-04-02
- Last modified
- 2026-07-24
- Assigner
- [email protected]
- CVSS 3.1 ([email protected])
- 4.8 MEDIUM — CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
- CVSS 3.1 ([email protected])
- 6.5 MEDIUM — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- Weaknesses
- CWE-130, CWE-135
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.
Affected configurations
• rack rack (< 2.2.23)
• rack rack (>= 3.0.0 < 3.1.21)
• rack rack (>= 3.2.0 < 3.2.6)