CVE-2026-39324

ruby-rack-session: Rack::Session is a session management implementation for Rack

CVE-2026-39324 is fixed in ruby-rack-session on 1 platform, first by ruby-rack-session 2.1.1-0.1ubuntu0.26.04.1, released April 7, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

Urgent
CVSS
9.8
critical
Exploitation
None reported
No vendor assessment
CISA KEV
Not listed
Not in the Known Exploited Vulnerabilities catalog
EPSS
0.0027
19th percentile

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.

Where it's fixed

ProductFixed inFixReleased
Linux
ruby-rack-session · Debian 13.5 (trixie) 2.1.1-0.1+deb13u1 DEBIAN-CVE-2026-39324 Apr 7, 2026
ruby-rack-session · Debian 14 2.1.1-0.2 DEBIAN-CVE-2026-39324 Apr 7, 2026
ruby-rack-session · Ubuntu 25.10 (questing) 2.1.1-0.1ubuntu0.1 ruby-rack-session 2.1.1-0.1ubuntu0.1 Apr 30, 2026
ruby-rack-session · Ubuntu 26.04.1 LTS (resolute) 2.1.1-0.1ubuntu0.26.04.1 ruby-rack-session 2.1.1-0.1ubuntu0.26.04.1 Apr 7, 2026

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