Vulnerability record · CVE-2025-6442 · published 25 June 2025

CVE-2025-6442: Ruby-lang webrick http request smuggling vulnerability

Ruby Lang · Webrick

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.

5.9 CVSS 3.1 Medium EPSS 0.50% · top 60.0% CWE-444 · HTTP request smuggling

5.9CVSS 3.1 base score

0.50%EPSS exploitation probability, 30 days

NoNot in CISA KEV

1Affected product versions listed by NVD

2References

17 Jun 2026Last modified by NVD

Description

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

Webrick Ruby Lang

References

Link	Tags
https://github.com/ruby/webrick/commit/ee60354bcb84ec33b9245e1d1aa6e1f7e8132101#diff-ad02984d873efb089aa51551bc6b7d307a5	Patch
https://www.zerodayinitiative.com/advisories/ZDI-25-414/	Third Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2025-6442), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.