CVE-2026-26962 MEDIUM

CVE-2026-26962: Rack: Header injection in multipart requests

Vendor Rack
Product rack
Weakness CWE-93 · CRLF injection
Published April 2, 2026
Last update April 3, 2026

CVSS base score

4.8/10
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Confidentiality Low
Integrity Low

CVSS vector

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

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

April 2, 2026 CVE published
April 3, 2026 Record updated