ruby-rack: Rack is a modular Ruby web server interface
CVE-2026-34835 is fixed in ruby-rack on 1 platform, first by ruby-rack 3.2.4-1ubuntu1.1, released April 2, 2026. It is not reported as exploited. Patch Radar priority: Routine.
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.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| ruby-rack · Debian 13.5 (trixie) | 3.1.20-0+deb13u2 | DEBIAN-CVE-2026-34835 | Apr 2, 2026 |
| ruby-rack · Debian 14 | 3.2.6-2 | DEBIAN-CVE-2026-34835 | Apr 2, 2026 |
| ruby-rack · Ubuntu 25.10 (questing) | 3.1.16-0.1ubuntu0.3 | ruby-rack 3.1.16-0.1ubuntu0.3 | Apr 30, 2026 |
| ruby-rack · Ubuntu 26.04.1 LTS (resolute) | 3.2.4-1ubuntu1.1 | ruby-rack 3.2.4-1ubuntu1.1 | Apr 2, 2026 |
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