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Vulnerabilities

Vulnerability · CVE-2025-6442

Ruby WEBrick read_header HTTP Request Smuggling Vulnerability.

Published Jun 25, 2025 · catalog updated Jun 25, 2025 · Ruby WEBrick

Check if you run it

No confirmed exploitation is on record for CVE-2025-6442. EPSS is 0.50%. Act only if a listed version of Ruby WEBrick is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium6.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.50%
Remediation
Vendor / distro source
Affected products
vendor Ruby WEBrick 1.8.1

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor Ruby WEBrick 1.8.11.8.1

How to fix CVE-2025-6442

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2025-6442. EPSS is 0.50%. Act only if a listed version of Ruby WEBrick is installed.

Which versions are affected?

Compare what you have installed with Ruby WEBrick 1.8.1 1.8.1. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.50%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Jun 25, 2025 · EUVD

    Detected

    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

  2. Jun 25, 2025 · EUVD

    Updated

    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

Sources

  • CVE.orgVulnerability recordCVE-2025-6442

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2025-6442

    30-day exploitation probability 0.50%

    first.org
  • EUVDVulnerability recordEUVD-2025-19113

    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 specif

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Oct 23, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.