Skip to content
CVE PROGRAM SOURCE RECORD9.3 Critical

CVE-2026-39324

Rack::Session::Cookie secrets: decrypt failure fallback enables secretless session forgery and Marshal deserialization

Description

Rack::Session is a session management implementation for Rack. From 2.0.0 to before 2.1.2, Rack::Session::Cookie incorrectly handles decryption failures when configured with secrets:. If cookie decryption fails, the implementation falls back to a default decoder instead of rejecting the cookie. This allows an unauthenticated attacker to supply a crafted session cookie that is accepted as valid session data without knowledge of any configured secret. Because this mechanism is used to load session state, an attacker can manipulate session contents and potentially gain unauthorized access. This vulnerability is fixed in 2.1.2.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

rack rack-session

  • >= 2.0.0, < 2.1.2affected

References