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Vulnerabilities / CVE-2026-39324

critical

CVE-2026-39324

github.com/rack/rack-session: Rack::Session: Unauthorized access via crafted session cookies

Published Modified CWE 287, 345, 502, 565
In the Trivy database since at least 24 Oct 2026, 07:11 UTCWhen it arrived before that build is not recorded.

Severity by source

NVD9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
GHSA9.1CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Red Hat10.0CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Trivy's own label is CRITICAL. Rated critical by NVD, GHSA, Red Hat. Rated lower by Ubuntu (medium).

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 packages and fixed versions

SourcePackageFixed in
rubygems::GitHub Security Advisory RubyGemsrack-session2.1.2
chainguardlogstash-8.19, logstash-9.0, logstash-9.1 and 16 more8.19.14-r3 and 15 more
debian 13ruby-rack-session2.1.1-0.1+deb13u1
debian 14ruby-rack-session2.1.1-0.2
echoruby-rack-session2.1.1-0.1+deb13u1
minimoslogstash-9.3, ruby3.4-rack-session, ruby4.0-rack-session9.3.4-r0 and 1 more
rapidfort debian 12ruby-rack-session0:2.1.1-0.1+deb13u1, 0:2.1.1-0.2
rapidfort debian 13ruby-rack-session0:2.1.1-0.1+deb13u1, 0:2.1.1-0.2
rapidfort ubuntu 20.04ruby-rack-session0:2.1.1-0.1ubuntu0.1
rapidfort ubuntu 22.04ruby-rack-session0:2.1.1-0.1ubuntu0.1
rapidfort ubuntu 24.04ruby-rack-session0:2.1.1-0.1ubuntu0.1
rubygems::Ruby Advisory Databaserack-session>= 2.1.2
Show all 39 entries from 15 sources
SourcePackageFixed in
rubygems::GitHub Security Advisory RubyGemsrack-session2.1.2
chainguardlogstash-8.198.19.14-r3
chainguardlogstash-9.09.0.8-r20
chainguardlogstash-9.19.1.10-r6
chainguardlogstash-9.29.2.8-r2
chainguardlogstash-9.39.3.3-r2
chainguardpact-broker-docker2.137.0.2.118.0-r4
chainguardpact-broker-docker-fips2.137.0.2.118.0-r2
chainguardruby3.2-rails-7.27.2.3.1-r2
chainguardruby3.2-rails-8.08.0.5-r0
chainguardruby3.2-rails-8.18.1.3-r3
chainguardruby3.3-rails-7.27.2.3.1-r4
chainguardruby3.3-rails-8.08.0.5-r3
chainguardruby3.3-rails-8.18.1.3-r4
chainguardruby3.4-rails-7.27.2.3.1-r2
chainguardruby3.4-rails-8.08.0.5-r2
chainguardruby3.4-rails-8.18.1.3-r4
chainguardruby4.0-rails-7.27.2.3.1-r3
chainguardruby4.0-rails-8.08.0.5-r1
chainguardruby4.0-rails-8.18.1.3-r3
debian 13ruby-rack-session2.1.1-0.1+deb13u1
debian 14ruby-rack-session2.1.1-0.2
echoruby-rack-session2.1.1-0.1+deb13u1
minimoslogstash-9.39.3.4-r0
minimosruby3.4-rack-session2.1.2-r0
minimosruby4.0-rack-session2.1.2-r0
rapidfort debian 12ruby-rack-session0:2.1.1-0.1+deb13u1, 0:2.1.1-0.2
rapidfort debian 13ruby-rack-session0:2.1.1-0.1+deb13u1, 0:2.1.1-0.2
rapidfort ubuntu 20.04ruby-rack-session0:2.1.1-0.1ubuntu0.1
rapidfort ubuntu 22.04ruby-rack-session0:2.1.1-0.1ubuntu0.1
rapidfort ubuntu 24.04ruby-rack-session0:2.1.1-0.1ubuntu0.1
rubygems::Ruby Advisory Databaserack-session>= 2.1.2
ubuntu 25.10ruby-rack-session2.1.1-0.1ubuntu0.1
ubuntu 26.04ruby-rack-session2.1.1-0.1ubuntu0.26.04.1
wolfilogstash-9.39.3.3-r2
wolfiruby3.2-rails-8.18.1.3-r3
wolfiruby3.3-rails-8.18.1.3-r4
wolfiruby3.4-rails-8.18.1.3-r4
wolfiruby4.0-rails-8.18.1.3-r3

References

All 9 references

Vulnerability data compiled from the Trivy vulnerability database (trivy-db, Aqua Security, Apache License 2.0), which aggregates third-party advisories. CVE records are published by The MITRE Corporation under the CVE Terms of Use; CVE is a trademark of MITRE. This product uses data from the NVD API but is not endorsed or certified by the NVD. Severity, titles and advisory data from the GitHub Advisory Database (CC BY 4.0), Red Hat security data (CC BY 4.0) and the other sources linked on each entry. Entries may be summarised or re-formatted; the linked original is the authoritative record.