CVE-2025-6442

25.06.2025, 17:15

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.

HTTP Request/Response Smuggling

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
NIST	NIST	5.9 MEDIUM	NETWORK	HIGH	NONE	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
zdi	CNA	6.5 MEDIUM				CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N
CISA-ADP	ADP	---				---

Base Score

CVSS 3.x

EPSS Score

Percentile: 13%

Vendor	Product	Version
ruby-lang	webrick	𝑥 < 1.8.2

𝑥

= Vulnerable software versions

Debian Releases

Debian Product

Codename

ruby-webrick

bookworm	no-dsa
forky	1.9.1-1 fixed
sid	1.9.1-1 fixed
trixie	1.9.1-1 fixed

Ubuntu Releases

Ubuntu Product

Codename

ruby-webrick

questing	Fixed 1.9.1-1 released
plucky	Fixed 1.8.1-1ubuntu1.1 released
oracular	ignored
noble	Fixed 1.8.1-1ubuntu0.2 released
jammy	Fixed 1.7.0-3ubuntu0.2 released

jruby

questing	not-affected
plucky	not-affected
noble	not-affected
jammy	dne
focal	needed
bionic	needed
xenial	needed
trusty	needed

ruby2.3

questing	dne
plucky	dne
noble	dne
jammy	dne
xenial	Fixed 2.3.1-2~ubuntu16.04.16+esm11 released

ruby2.5

questing	dne
plucky	dne
noble	dne
jammy	dne
bionic	Fixed 2.5.1-1ubuntu1.16+esm6 released

ruby2.7

questing	dne
plucky	dne
noble	dne
jammy	dne
focal	Fixed 2.7.0-5ubuntu1.18+esm3 released

Common Weakness Enumeration

CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.

References

https://github.com/ruby/webrick/commit/ee60354bcb84ec33b9245e1d1aa6e1f7e8132101#diff-ad02984d873efb089aa51551bc6b7d307a53e0ba1ac439e91d69c2e58a478864

https://www.zerodayinitiative.com/advisories/ZDI-25-414/