CVE-2026-34831 (GCVE-0-2026-34831)

Vulnerability from cvelistv5 – Published: 2026-04-02 16:43 – Updated: 2026-04-03 17:48
VLAI
Title
Rack: Content-Length mismatch in Rack::Files error responses
Summary
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.
Severity
4.8 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-04-03 17:43 UTC
CWE
  • CWE-130 - Improper Handling of Length Parameter Inconsistency
  • CWE-135 - Incorrect Calculation of Multi-Byte String Length
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 8035 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
rack rack Affected: < 2.2.23
Affected: >= 3.0.0.beta1, < 3.1.21
Affected: >= 3.2.0, < 3.2.6
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

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