CVE-2026-34835

MEDIUM EPSS 9.1%
Published Apr 2, 20262mo ago · Modified Jun 17, 20261w ago
6.5 CVSS 3.1
Medium
Find Similar
Published Apr 2, 2026 2mo ago
Last Modified Jun 17, 2026 1w ago

Description

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 Details

Base Score
6.5
Exploitability
3.9
Impact
2.5
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope Unchanged
Confidentiality Low
Integrity Low
Availability None

Threat Intelligence

EPSS Exploit Probability
9.1% percentile
Exploit & Patch Status
Public Exploit Known
No Patch Available

Weaknesses 1

CWE-1286

Affected Products 2

VendorProductVersionRange
rackrack*≥3.0.0  –  <3.1.21
rackrack*≥3.2.0  –  <3.2.6

References 1

  • github.com https://github.com/rack/rack/security/advisories/GHSA-g2pf-xv49-m2h5
    ExploitMitigationVendor Advisory

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.