Advisory Details

June 23rd, 2025

Ruby WEBrick read_header HTTP Request Smuggling Vulnerability

ZDI-25-414
ZDI-CAN-21876

CVE ID CVE-2025-6442
CVSS SCORE 6.5, AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N
AFFECTED VENDORS Ruby
AFFECTED PRODUCTS WEBrick
VULNERABILITY DETAILS

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.
ADDITIONAL DETAILS Ruby has issued an update to correct this vulnerability. More details can be found at:
https://github.com/ruby/webrick/commit/ee60354bcb84ec33b9245e1d1aa6e1f7e8132101#diff-ad02984d873efb089aa51551bc6b7d307a53e0ba1ac439e91d69c2e58a478864
DISCLOSURE TIMELINE
  • 2023-09-13 - Vulnerability reported to vendor
  • 2025-06-23 - Coordinated public release of advisory
  • 2025-06-23 - Advisory Updated
CREDIT yadhukrishnam
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