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.

Metrics

No CVSS v4.0

Attack Vector Network

Attack Complexity High

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact High

Availability Impact None

User Interaction None

Attack Vector Network

Attack Complexity High

Privileges Required None

Scope Unchanged

Confidentiality Impact Low

Integrity Impact High

Availability Impact None

User Interaction None

No CVSS v2

This CVE is not in the KEV list.

Exploitation none

Automatable no

Technical Impact partial

Affected Vendors & Products

Vendors Products
Ruby
  • Webrick
Ruby-lang
  • Webrick

Configuration 1 [-]

cpe:2.3:a:ruby-lang:webrick:*:*:*:*:*:ruby:*:*

No data.

References
Link Providers
https://github.com/ruby/webrick/commit/ee60354bcb84ec33b9245e1d1aa6e1f7e8132101#diff-ad02984d873efb089aa51551bc6b7d307a53e0ba1ac439e91d69c2e58a478864 cve-icon cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2025-6442 cve-icon
https://www.cve.org/CVERecord?id=CVE-2025-6442 cve-icon
https://www.zerodayinitiative.com/advisories/ZDI-25-414/ cve-icon cve-icon cve-icon
History

Mon, 18 Aug 2025 16:00:00 +0000

Type Values Removed Values Added
First Time appeared Ruby-lang
Ruby-lang webrick
CPEs cpe:2.3:a:ruby-lang:webrick:*:*:*:*:*:ruby:*:*
Vendors & Products Ruby-lang
Ruby-lang webrick
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N'}

Wed, 16 Jul 2025 13:45:00 +0000

Type Values Removed Values Added
Metrics epss

{'score': 0.00066}

 epss

{'score': 0.00049}

Fri, 27 Jun 2025 00:30:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

 threat_severity

Moderate

Wed, 25 Jun 2025 21:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Wed, 25 Jun 2025 17:15:00 +0000

Type Values Removed Values Added
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.
Title Ruby WEBrick read_header HTTP Request Smuggling Vulnerability
Weaknesses CWE-444
References
Metrics cvssV3_0

{'score': 6.5, 'vector': 'CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N'}
cve-icon MITRE

Status: PUBLISHED

Assigner: zdi

Published: 2025-06-25T16:52:24.625Z

Updated: 2025-06-25T20:42:41.093Z

Reserved: 2025-06-20T17:14:36.566Z

Link: CVE-2025-6442

cve-icon Vulnrichment

Updated: 2025-06-25T20:42:37.898Z

cve-icon NVD

Status : Analyzed

Published: 2025-06-25T17:15:40.117

Modified: 2025-08-18T15:49:38.773

Link: CVE-2025-6442

cve-icon Redhat

Severity : Moderate

Publid Date: 2025-06-25T16:52:24Z

Links: CVE-2025-6442 - Bugzilla