cbcvebase.
CVE-2026-34835
published 2026-04-02

CVE-2026-34835: 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…

PriorityP337medium6.5CVSS 3.1
AVNACLPRNUINSUCLILAN
EPSS
0.19%
9.2th percentile
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.

Affected

7 ranges
VendorProductVersion rangeFixed in
debianruby-rack< ruby-rack 3.2.6-2 (sid)ruby-rack 3.2.6-2 (sid)
rackrack
rackrack
rackrack>= 3.0.0 < 3.1.213.1.21
rackrack>= 3.0.0.beta1 < 3.1.213.1.21
rackrack>= 3.2.0 < 3.2.63.2.6
rackrack>= 3.2.0 < 3.2.63.2.6

CVSS provenance

nvdv3.16.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
osv6.5MEDIUM
vendor_debian4.8MEDIUM
vendor_redhat4.8MEDIUM
vendor_ubuntu3.7LOW
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