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Medium severity · published Jun 25, 2025
CVE-2025-6442
Ruby WEBrick read_header HTTP Request Smuggling Vulnerability
5.9
CVSS
0.5%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
None
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 42% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
WE
Webrick · Ruby-lang
before 1.8.2 · source: NVD
Affected product
WE
Webrick
Ruby-lang
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-6442
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-6442
Patch
https://github.com/ruby/webrick/commit/ee60354bcb84ec33b9245e1d1aa6e1f7e8132101#diff-ad02984d873efb089aa51551bc6b7d307a53e0ba1ac439e91d69c2e58a478864
Third Party Advisory
https://www.zerodayinitiative.com/advisories/ZDI-25-414/
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