Ruby WEBrick read_headers method can lead to HTTP Request/Response Smuggling

MEDIUM 5.9CVE-2025-6442 · GHSA-r995-q44h-hr64 · Published 25/06/2025 · updated 17/06/2026

Package	Affected versions	Patched versions
webrick RubyGems	`< 1.8.2`	`1.8.2`
webrick ruby-lang	`< 1.8.2`	`1.8.2`

Description

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.

NVD 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.

References

nvd.nist.gov/vuln/detail/CVE-2025-6442 · ADVISORY
ruby/webrick commit ee60354 · WEB
ruby/webrick · PACKAGE
rubysec/ruby-advisory-db · WEB
zerodayinitiative.com/advisories/ZDI-25-414 · WEB
zerodayinitiative.com/advisories/ZDI-25-414 · Third Party Advisory

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Package

Affected versions

Patched versions

webrick

RubyGems

< 1.8.2

1.8.2

webrick

ruby-lang

< 1.8.2

1.8.2

Description

NVD description