CVE-2023-37464 in cjose
Summary
by MITRE • 07/15/2023
OpenIDC/cjose is a C library implementing the Javascript Object Signing and Encryption (JOSE). The AES GCM decryption routine incorrectly uses the Tag length from the actual Authentication Tag provided in the JWE. The spec says that a fixed length of 16 octets must be applied. Therefore this bug allows an attacker to provide a truncated Authentication Tag and to modify the JWE accordingly. Users should upgrade to a version >= 0.6.2.2. Users unable to upgrade should avoid using AES GCM encryption and replace it with another encryption algorithm (e.g. AES CBC).
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Analysis
by VulDB Data Team • 06/21/2025
The vulnerability identified as CVE-2023-37464 affects the OpenIDC/cjose C library, which implements JavaScript Object Signing and Encryption (JOSE) standards for secure web communications. This library serves as a critical component in applications requiring secure token handling and encryption operations, particularly within identity and access management systems. The flaw resides in the AES GCM decryption routine where the implementation fails to properly validate authentication tag lengths according to established cryptographic standards. This represents a fundamental deviation from the JOSE specification requirements and creates a significant security weakness that could be exploited by malicious actors to manipulate encrypted data without detection.
The technical implementation error stems from the incorrect handling of authentication tags during the AES GCM decryption process. According to the JOSE specification, authentication tags must consistently use a fixed length of 16 octets regardless of the actual tag provided in the JWE structure. However, the vulnerable implementation incorrectly processes the tag length from the provided authentication tag rather than enforcing the mandated 16-octet standard. This deviation allows attackers to craft malicious JWE structures where they can truncate the authentication tag to arbitrary lengths while simultaneously modifying the encrypted content. The vulnerability essentially undermines the integrity protection mechanisms that GCM encryption is designed to provide, creating a scenario where authenticated encryption can be bypassed through carefully constructed input manipulation.
The operational impact of this vulnerability extends beyond simple cryptographic weakness to encompass potential data compromise and system integrity breaches. Attackers exploiting this flaw could manipulate JWE structures to inject malicious content while maintaining apparent authenticity, potentially leading to unauthorized access to protected resources, data exfiltration, or privilege escalation within systems relying on cjose for secure token handling. The vulnerability affects systems using AES GCM encryption within the JOSE framework, which is commonly deployed in OAuth 2.0 implementations, OpenID Connect protocols, and various single sign-on solutions. Organizations utilizing this library for security-critical operations face significant risk of undetected data manipulation, particularly in environments where JWE tokens are used for authentication, authorization, or sensitive data transmission.
Security mitigations for CVE-2023-37464 primarily focus on version upgrades to cjose 0.6.2.2 or later, which implements correct authentication tag handling according to JOSE specifications. This represents a direct patch addressing the core implementation flaw and restoring proper cryptographic behavior. For organizations unable to immediately upgrade, the recommended workaround involves avoiding AES GCM encryption entirely and transitioning to alternative encryption algorithms such as AES CBC, which do not exhibit the same tag length handling vulnerability. This mitigation strategy aligns with defense-in-depth principles and follows established cryptographic best practices for avoiding known weak implementations. The vulnerability demonstrates the critical importance of strict adherence to cryptographic standards and the potential consequences of implementation deviations, particularly in security-critical libraries that form the foundation of modern identity and access management systems. Organizations should conduct thorough vulnerability assessments to identify all systems utilizing the affected library and implement appropriate remediation measures to prevent exploitation attempts.
This vulnerability maps to CWE-327 (Use of a Broken or Risky Cryptographic Algorithm) and CWE-328 (Use of Weak Hash) within the Common Weakness Enumeration framework, reflecting the fundamental cryptographic implementation flaws that compromise security assurances. From an ATT&CK perspective, this weakness could be leveraged as part of a broader attack chain involving credential manipulation or privilege escalation, particularly in environments where JWE tokens are used for authentication purposes. The vulnerability exemplifies how seemingly minor implementation details in cryptographic libraries can create significant security risks, emphasizing the need for rigorous security testing and adherence to established cryptographic standards in all security-critical software components.