CVE-2026-39324: CWE-287: Improper Authentication in rack rack-session
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.
AI Analysis
Technical Summary
Rack::Session::Cookie in rack-session versions >= 2.0.0 and < 2.1.2 improperly handles decryption failures by falling back to a default decoder rather than rejecting invalid cookies. This behavior allows attackers without knowledge of the configured secret to craft session cookies that the system accepts as valid, potentially leading to unauthorized access by manipulating session state. The issue is classified under CWE-287 (Improper Authentication) and related weaknesses. The vulnerability has a CVSS 4.0 score of 9.3, indicating critical severity. The flaw is resolved in version 2.1.2.
Potential Impact
An attacker can bypass authentication mechanisms by supplying crafted session cookies that are accepted as valid despite lacking the secret key. This can lead to unauthorized access and manipulation of session data, compromising application security and user data integrity. The vulnerability affects all deployments using rack-session versions from 2.0.0 up to but not including 2.1.2.
Mitigation Recommendations
Upgrade rack-session to version 2.1.2 or later, where this vulnerability is fixed. Since no official patch link or advisory is provided, users should verify the version in use and apply the update accordingly. Patch status is not explicitly confirmed beyond the stated fixed version; therefore, check the vendor's official channels for the latest remediation guidance.
CVE-2026-39324: CWE-287: Improper Authentication in rack rack-session
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.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Rack::Session::Cookie in rack-session versions >= 2.0.0 and < 2.1.2 improperly handles decryption failures by falling back to a default decoder rather than rejecting invalid cookies. This behavior allows attackers without knowledge of the configured secret to craft session cookies that the system accepts as valid, potentially leading to unauthorized access by manipulating session state. The issue is classified under CWE-287 (Improper Authentication) and related weaknesses. The vulnerability has a CVSS 4.0 score of 9.3, indicating critical severity. The flaw is resolved in version 2.1.2.
Potential Impact
An attacker can bypass authentication mechanisms by supplying crafted session cookies that are accepted as valid despite lacking the secret key. This can lead to unauthorized access and manipulation of session data, compromising application security and user data integrity. The vulnerability affects all deployments using rack-session versions from 2.0.0 up to but not including 2.1.2.
Mitigation Recommendations
Upgrade rack-session to version 2.1.2 or later, where this vulnerability is fixed. Since no official patch link or advisory is provided, users should verify the version in use and apply the update accordingly. Patch status is not explicitly confirmed beyond the stated fixed version; therefore, check the vendor's official channels for the latest remediation guidance.
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: 4/7/2026, 6:32:07 PM
Last updated: 4/7/2026, 10:48:42 PM
Views: 6
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