CVE-2026-39324: CWE-287: Improper Authentication in rack rack-session
CVE-2026-39324 is a critical improper authentication vulnerability in rack-session versions 2. 0. 0 up to but not including 2. 1. 2. The vulnerability arises because Rack::Session::Cookie incorrectly handles decryption failures by falling back to a default decoder instead of rejecting the cookie. This flaw allows an unauthenticated attacker to supply a crafted session cookie that is accepted as valid without knowing any configured secret, enabling manipulation of session contents and potential unauthorized access. The issue is fixed in version 2. 1. 2.
AI Analysis
Technical Summary
Rack::Session::Cookie in rack-session versions from 2.0.0 to before 2.1.2 improperly handles cookie decryption failures when configured with secrets:. Instead of rejecting cookies that fail decryption, it falls back to a default decoder, allowing attackers to craft session cookies accepted as valid session data without knowledge of secrets. This improper authentication vulnerability (CWE-287) can lead to unauthorized access by manipulating session state. The vulnerability has a CVSS 4.0 score of 9.3 (critical) and is fixed in version 2.1.2.
Potential Impact
An attacker can bypass authentication by supplying a crafted session cookie that is accepted as valid, potentially manipulating session contents and gaining unauthorized access to the application relying on rack-session for session management. This compromises the integrity and confidentiality of user sessions.
Mitigation Recommendations
Upgrade rack-session to version 2.1.2 or later, where this vulnerability is fixed. Patch status is not explicitly stated in the vendor advisory content, but the description confirms the fix in 2.1.2. No other mitigations are indicated.
CVE-2026-39324: CWE-287: Improper Authentication in rack rack-session
Description
CVE-2026-39324 is a critical improper authentication vulnerability in rack-session versions 2. 0. 0 up to but not including 2. 1. 2. The vulnerability arises because Rack::Session::Cookie incorrectly handles decryption failures by falling back to a default decoder instead of rejecting the cookie. This flaw allows an unauthenticated attacker to supply a crafted session cookie that is accepted as valid without knowing any configured secret, enabling manipulation of session contents and potential unauthorized access. The issue is fixed in version 2. 1. 2.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Rack::Session::Cookie in rack-session versions from 2.0.0 to before 2.1.2 improperly handles cookie decryption failures when configured with secrets:. Instead of rejecting cookies that fail decryption, it falls back to a default decoder, allowing attackers to craft session cookies accepted as valid session data without knowledge of secrets. This improper authentication vulnerability (CWE-287) can lead to unauthorized access by manipulating session state. The vulnerability has a CVSS 4.0 score of 9.3 (critical) and is fixed in version 2.1.2.
Potential Impact
An attacker can bypass authentication by supplying a crafted session cookie that is accepted as valid, potentially manipulating session contents and gaining unauthorized access to the application relying on rack-session for session management. This compromises the integrity and confidentiality of user sessions.
Mitigation Recommendations
Upgrade rack-session to version 2.1.2 or later, where this vulnerability is fixed. Patch status is not explicitly stated in the vendor advisory content, but the description confirms the fix in 2.1.2. No other mitigations are indicated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-04-06T19:31:07.266Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69d549ecaaed68159a47390c
Added to database: 4/7/2026, 6:16:12 PM
Last enriched: 4/15/2026, 12:37:53 PM
Last updated: 5/22/2026, 5:17:20 PM
Views: 795
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