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 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.

CVSS v3 4.8 MEDIUM

4.8^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.2 / Impact : 2.5

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact LOW

Integrity Impact LOW

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/rack/rack/security/advisories/GHSA-g2pf-xv49-m2h5	Vendor Advisory Exploit Mitigation

Configurations

Configuration 1 (hide)

OR	cpe:2.3:a:rack:rack::::::ruby::*
	cpe:2.3:a:rack:rack::::::ruby::*

History

03 Apr 2026, 19:32

Type	Values Removed	Values Added
CPE		cpe:2.3:a:rack:rack::::::ruby::*
References	~~() https://github.com/rack/rack/security/advisories/GHSA-g2pf-xv49-m2h5 -~~	() https://github.com/rack/rack/security/advisories/GHSA-g2pf-xv49-m2h5 - Vendor Advisory, Exploit, Mitigation
First Time		Rack rack Rack

02 Apr 2026, 18:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-04-02 18:16

Updated : 2026-04-03 19:32

NVD link : CVE-2026-34835

Mitre link : CVE-2026-34835

CVE.ORG link : CVE-2026-34835

JSON object : View

Products Affected

rack

rack

CWE

CWE-1286

Improper Validation of Syntactic Correctness of Input

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