CVE-2026-34835 (GCVE-0-2026-34835)

Vulnerability from cvelistv5 – Published: 2026-04-02 17:09 – Updated: 2026-04-02 17:44
VLAI
Title
Rack: `Rack::Request` accepts invalid Host characters, enabling host allowlist bypass.
Summary
Rack is a modular Ruby web server interface. From versions 3.0.0.beta1 to before 3.1.21, and 3.2.0 to before 3.2.6, Rack::Request parses the Host header using an AUTHORITY regular expression that accepts characters not permitted in RFC-compliant hostnames, including /, ?, #, and @. Because req.host returns the full parsed value, applications that validate hosts using naive prefix or suffix checks can be bypassed. This can lead to host header poisoning in applications that use req.host, req.url, or req.base_url for link generation, redirects, or origin validation. This issue has been patched in versions 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 2026-04-02 17:43 UTC
CWE
  • CWE-1286 - Improper Validation of Syntactic Correctness of Input
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 7763 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
rack rack 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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