Rack up to 3.2.5 HTTP Response Header Rack::Multipart crlf injection

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Rack up to 3.2.5. This impacts the function Rack::Multipart of the component HTTP Response Header Handler. Performing a manipulation results in crlf injection. This vulnerability is reported as CVE-2026-26962. The attack is possible to be carried out remotely. No exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Rack up to 3.2.5. It has been classified as problematic. This affects the function Rack::Multipart of the component HTTP Response Header Handler. The manipulation with an unknown input leads to a crlf injection vulnerability. CWE is classifying the issue as CWE-93. The product uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs. This is going to have an impact on integrity. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-26962 since 02/16/2026. The exploitability is told to be difficult. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are known, but no exploit is available.

Upgrading to version 3.2.6 eliminates this vulnerability.

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Productinfo

Name

• Rack

Version

• 3.2.0
• 3.2.1
• 3.2.2
• 3.2.3
• 3.2.4
• 3.2.5

Website

• Product: https://github.com/rack/rack/

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