CVE-2015-2951 in JWT
Summary
by MITRE
JWT.php in F21 JWT before 2.0 allows remote attackers to bypass signature verification via crafted tokens.
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Analysis
by VulDB Data Team • 05/20/2022
The vulnerability identified as CVE-2015-2951 affects the F21 JWT library version 2.0 and earlier, representing a critical security flaw in JSON Web Token implementation that undermines the fundamental integrity protection mechanisms of the token-based authentication system. This issue resides within the JWT.php file and specifically targets the signature verification process that is essential for ensuring token authenticity and preventing unauthorized access to protected resources.
The technical flaw stems from improper validation of JSON Web Token signatures, allowing malicious actors to construct specially crafted tokens that appear valid to the system despite lacking proper cryptographic authentication. Attackers can exploit this weakness by creating tokens with modified payload data or altered signature parameters that bypass the library's verification checks. The vulnerability essentially creates a condition where the system accepts tokens that should be rejected due to invalid or missing signatures, thereby enabling unauthorized access to systems and data that would normally be protected by proper authentication mechanisms.
This vulnerability has significant operational impact across various security domains as it undermines the core security model of token-based authentication systems. When exploited, attackers can gain unauthorized access to protected resources, escalate privileges, and potentially move laterally within networks where JWT tokens are used for authentication. The flaw affects any system relying on the F21 JWT library for token validation, potentially compromising user sessions, sensitive data access, and overall system integrity. The attack surface extends beyond simple authentication bypass to include potential data exfiltration and privilege escalation scenarios that could severely impact organizational security posture.
Organizations utilizing the affected F21 JWT library should immediately upgrade to version 2.0 or later to remediate this vulnerability. Additional mitigations include implementing proper input validation, monitoring for suspicious token patterns, and ensuring that all authentication systems enforce strict signature verification requirements. The vulnerability aligns with CWE-347 weakness category related to improper validation of cryptographic signatures and can be categorized under ATT&CK technique T1566 for credential access through valid accounts. Security teams should also consider implementing token integrity monitoring and regular security assessments to detect potential exploitation attempts and maintain robust authentication security controls throughout their infrastructure.