PT-2026-29857 · Rack · Rack

Th4S1S · Published 2026-04-02 · Updated 2026-04-02 · CVE-2026-34835

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. 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.

Fix

Weakness Enumeration

CWE-1286

Related Identifiers

CVE-2026-34835

Affected Products

Rack

References · 2

• https://nvd.nist.gov/vuln/detail/CVE-2026-34835 · Security Note
• https://github.com/rack/rack/security/advisories/GHSA-g2pf-xv49-m2h5 · Note