Vulnerability in Rack
CVE-2026-26962
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.
Vulnerability class: CRLF Injection
EPSS: 0.002 (13.5th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 4.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N.
Affected products
- Rack — versions >= 3.2.0, < 3.2.6
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Mitigation, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-26962?
- CVE-2026-26962 is a medium-severity vulnerability in Rack, classified under CRLF Injection. CVSS score: 4.8/10. Published 2026-04-02.
- How severe is CVE-2026-26962?
- Medium severity. CVSS v3 base score is 4.8 out of 10.