Is CVE-2025-6442 in the CISA KEV catalog?

No. CVE-2025-6442 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2025-6442?

CVE-2025-6442 has a CVSS v3 base score of 5.9 (MEDIUM).

What is the EPSS score for CVE-2025-6442?

CVE-2025-6442 has an EPSS score of 0.42% (34th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2025-6442?

Upgrade ruby-webrick on debian 13 to 1.9.1-1 or later. Fixes are available for 8 affected products.

CVE & CISA-KEV Catalog

CVE-2025-6442

MEDIUM

5.9

CVSS v3

NVD

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.

CWE-444

How to fix

Remediation Available

ruby-webrickDebian

Fixed in:1.9.1-1CVE-2025-6442

libruby2.3Ubuntu

Fixed in:2.3.1-2~ubuntu16.04.16+esm11USN-7840-1

libruby2.5Ubuntu

Fixed in:2.5.1-1ubuntu1.16+esm6USN-7840-1

libruby2.7Ubuntu

Fixed in:2.7.0-5ubuntu1.18+esm3USN-7840-1

ruby-webrickUbuntu

Fixed in:1.7.0-3ubuntu0.2USN-7709-1

Fixed in:1.8.1-1ubuntu0.2USN-7709-1

ruby2.3Ubuntu

Fixed in:2.3.1-2~ubuntu16.04.16+esm11USN-7840-1

ruby2.5Ubuntu

Fixed in:2.5.1-1ubuntu1.16+esm6USN-7840-1

ruby2.7Ubuntu

Fixed in:2.7.0-5ubuntu1.18+esm3USN-7840-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityHigh

AvailabilityNone

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

Exploit Intelligence

0.42%probability of exploitation in 30 days

34thpercentile

Low risk: more likely to be exploited than 34% of all known CVEs.

References

Patch1

github.com

Third-Party Advisory1

zerodayinitiative.com

Related Vulnerabilities

Other CWE-444 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2022-22536	Critical	10.0	98%	KEV	-
CVE-2025-61884	High	7.5	98%	KEV + Ransom	-
CVE-2020-9490	High	7.5	90%	-	Fix
CVE-2023-41265	Critical	9.6	85%	KEV + Ransom	-
CVE-2023-25690	Critical	9.8	84%	-	Fix
CVE-2022-32214	Medium	6.5	78%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-08-18.