CVE & CISA-KEV Catalog

CVE-2026-26962

MEDIUM
4.8
CVSS v3
NVD

Description

Rack is a modular Ruby web server interface. From version 3.2.0 to before version 3.2.6, Rack::Multipart::Parser unfolds folded multipart part headers incorrectly. When a multipart header contains an obs-fold sequence, Rack preserves the embedded CRLF in parsed parameter values such as filename or name instead of removing the folded line break during unfolding. As a result, applications that later reuse those parsed values in HTTP response headers may be vulnerable to downstream header injection or response splitting. This issue has been patched in version 3.2.6.

How to fix

Remediation Available
ruby-rackDebian
Fixed in:3.2.6-2CVE-2026-26962
librack-rubyUbuntu
Fixed in:1.5.2-3+deb8u3ubuntu1~esm11USN-8182-1
librack-ruby1.8Ubuntu
Fixed in:1.5.2-3+deb8u3ubuntu1~esm11USN-8182-1
librack-ruby1.9.1Ubuntu
Fixed in:1.5.2-3+deb8u3ubuntu1~esm11USN-8182-1
ruby-rackUbuntu
Fixed in:1.5.2-3+deb8u3ubuntu1~esm11USN-8182-1
Fixed in:1.6.4-3ubuntu0.2+esm10USN-8182-1
Fixed in:1.6.4-4ubuntu0.2+esm10USN-8182-1
Fixed in:2.0.7-2ubuntu0.1+esm10USN-8182-1
Fixed in:2.1.4-5ubuntu1.2+esm3USN-8182-1
Fixed in:2.2.7-1ubuntu0.7USN-8182-1
Fixed in:3.1.16-0.1ubuntu0.3USN-8182-1

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

ConfidentialityLow
IntegrityLow
AvailabilityNone

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

Exploit Intelligence

0.23%probability of exploitation in 30 days
13thpercentile

Low risk: more likely to be exploited than 13% of all known CVEs.

References

Vendor Advisory1

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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 2026-04-21.