ADVISORIES

• CVE-2025-6442 (NVD)
• GHSA-r995-q44h-hr64

GEM

webrick

SEVERITY

CVSS v3.x: 6.5 (Medium)

PATCHED VERSIONS

• >= 1.8.2

DESCRIPTION

Ruby WEBrick read_header HTTP Request Smuggling Vulnerability

This vulnerability allows remote attackers to smuggle arbitrary HTTP requests on affected installations of Ruby WEBrick. This issue is exploitable when the product is deployed behind an HTTP proxy that fulfills specific conditions.

The specific flaw exists within the read_headers method. The issue results from the inconsistent parsing of terminators of HTTP headers. An attacker can leverage this vulnerability to smuggle arbitrary HTTP requests. Was ZDI-CAN-21876.

RELATED

• https://nvd.nist.gov/vuln/detail/CVE-2025-6442
• https://github.com/ruby/webrick/commit/ee60354bcb84ec33b9245e1d1aa6e1f7e8132101#diff-ad02984d873efb089aa51551bc6b7d307a53e0ba1ac439e91d69c2e58a478864
• https://www.zerodayinitiative.com/advisories/ZDI-25-414
• https://github.com/advisories/GHSA-r995-q44h-hr64