What’s Vulnerable › Vulnerabilities
CVE-2026-26962: Rack: Header injection in multipart requests
- Severity: medium (CVSS 6.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.2% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-04-02 · updated 2026-07-24
- Weakness: CWE-93
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.
Affected products
- rack: from 3.2.0 before 3.2.6 — fixed in 3.2.6
How to fix
Upgrade to a fixed version: rack 3.2.6. Check the vendor advisory for mitigations.
References
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