CVE & CISA-KEV Catalog

CVE-2008-3656

HIGHEPSS 99th pctl
7.8
CVSS v2
NVD

Description

Algorithmic complexity vulnerability in the WEBrick::HTTPUtils.split_header_value function in WEBrick::HTTP::DefaultFileHandler in WEBrick in Ruby 1.8.5 and earlier, 1.8.6 through 1.8.6-p286, 1.8.7 through 1.8.7-p71, and 1.9 through r18423 allows context-dependent attackers to cause a denial of service (CPU consumption) via a crafted HTTP request that is processed by a backtracking regular expression.

How to fix

Remediation Available
ruby4Red Hat / RHEL
Fixed in:0-main@aarch64RHSA-2026:8838
Fixed in:0-main@srcRHSA-2026:8838
Fixed in:0-main@x86_64RHSA-2026:8838
Fixed in:0-main@noarchRHSA-2026:8838
ruby4Rocky
Fixed in:0-main@aarch64RHSA-2026:8838
Fixed in:0-main@srcRHSA-2026:8838
Fixed in:0-main@x86_64RHSA-2026:8838
Fixed in:0-main@noarchRHSA-2026:8838

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

CVSS v2 Vector

No CVSS vector data available.

Exploit Intelligence

70.20%probability of exploitation in 30 days
99thpercentile

Very high risk: more likely to be exploited than 99% of all known CVEs.

References

Related Vulnerabilities

Other CWE-399 (Resource Management Errors) vulnerabilities, ordered by exploit likelihood. View all

CVESeverityCVSSEPSSExploitedFix
CVE-2009-3103High10.090%--
CVE-2009-0075High9.385%--
CVE-2005-1790Low2.683%--
CVE-2010-0806High8.882%KEV-
CVE-2009-2526High7.882%--
CVE-2015-1868High7.882%-Fix

Common questions

How do I fix CVE-2008-3656?

Published advisories record a fix for 2 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.

Is CVE-2008-3656 being actively exploited?

Not that we know of. CVE-2008-3656 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 70.2% is the estimated probability that it will be exploited in the next 30 days. That is higher than 99% of all scored CVEs.

How severe is CVE-2008-3656?

CVE-2008-3656 has a CVSS v2 base score of 7.8, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2008-3656 affect?

Published advisories record a fix for ruby4 (Red Hat / RHEL), ruby4 (Rocky). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

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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 2026-04-23.