CVE-2015-2964 in JOSE
Summary
by MITRE
NAMSHI | JOSE 5.0.0 and earlier allows remote attackers to bypass signature verification via crafted tokens in a JSON Web Tokens (JWT) header.
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Analysis
by VulDB Data Team • 05/03/2019
The vulnerability described in CVE-2015-2964 affects the NAMSHI JOSE library version 5.0.0 and earlier, which is a popular implementation for handling JSON Web Tokens in PHP applications. This security flaw represents a critical weakness in the library's token validation mechanism that could allow attackers to bypass crucial signature verification checks. The vulnerability specifically targets the JWT header processing component where the library fails to properly validate the signature algorithm used in the token, creating a path for malicious actors to craft tokens that appear legitimate but contain forged signatures.
The technical implementation flaw stems from the library's inadequate handling of the algorithm field within the JWT header structure. When processing JWT tokens, the NAMSHI JOSE library does not properly enforce the expected cryptographic algorithm, allowing attackers to manipulate the header to specify a different algorithm or even omit critical signature verification parameters. This weakness enables what is known as an algorithm confusion attack where the library accepts tokens signed with a weak or inappropriate algorithm, effectively rendering the signature verification mechanism useless. The vulnerability falls under CWE-347, which specifically addresses improper verification of cryptographic signatures, and aligns with ATT&CK technique T1552.001 for unsecured credentials and T1552.002 for credentials in files.
The operational impact of this vulnerability is severe as it allows remote attackers to forge JWT tokens without possessing the legitimate signing key. Attackers can create malicious tokens that bypass authentication mechanisms, potentially gaining unauthorized access to protected resources, modifying user permissions, or executing privilege escalation attacks. The vulnerability affects web applications that rely on JWT for authentication and authorization, making it particularly dangerous in environments where sensitive data or administrative functions are protected by token-based access controls. This flaw undermines the fundamental security properties of JWT implementations, as the integrity and authenticity guarantees that JWTs are designed to provide become compromised.
Organizations using affected versions of the NAMSHI JOSE library should immediately upgrade to version 5.0.1 or later, which contains the necessary patches to address the signature verification bypass. Security teams should conduct thorough audits of all applications utilizing this library to identify potential token manipulation vulnerabilities and implement additional monitoring for suspicious authentication patterns. The mitigation strategy should include implementing proper algorithm validation checks, ensuring that only explicitly trusted algorithms are accepted, and maintaining comprehensive logging of authentication attempts to detect potential exploitation attempts. Organizations should also consider implementing additional security layers such as token binding or short-lived tokens to reduce the impact window if the vulnerability is exploited.