CVE-2016-5429 in jose-php
Summary
by MITRE
jose-php before 2.2.1 does not use constant-time operations for HMAC comparison, which makes it easier for remote attackers to obtain sensitive information via a timing attack, related to JWE.php and JWS.php.
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Analysis
by VulDB Data Team • 09/14/2022
The vulnerability identified as CVE-2016-5429 affects the jose-php library version 2.2.1 and earlier, presenting a critical security flaw that undermines cryptographic integrity through timing attacks. This issue specifically targets the library's implementation of HMAC (Hash-based Message Authentication Code) comparison operations within the JWE.php and JWS.php modules. The flaw stems from the library's failure to employ constant-time algorithms when comparing HMAC values, creating measurable timing variations that can be exploited by attackers to infer sensitive cryptographic information.
The technical root cause of this vulnerability lies in the implementation of HMAC comparison functions that do not execute in constant time regardless of input values. When comparing HMAC signatures, traditional implementations may terminate early when encountering differing bytes, creating timing differences that can be quantified and analyzed. This behavior directly violates the fundamental security principle that cryptographic operations should exhibit consistent execution times to prevent timing-based information leakage. The vulnerability maps to CWE-208, which specifically addresses timing attacks that can lead to information disclosure through timing variations in cryptographic implementations.
Attackers can leverage this vulnerability through carefully crafted timing measurements to perform side-channel attacks against the jose-php library. By analyzing the time taken to process different HMAC values, an attacker can gradually deduce the correct HMAC signature, ultimately compromising the security of JSON Web Encryption and JSON Web Signature implementations. This type of attack falls under the ATT&CK technique T1214, which involves credential access through the exploitation of timing variations in cryptographic operations. The impact extends beyond simple information disclosure, as compromised HMAC values can lead to unauthorized access to protected resources, data tampering, and potential privilege escalation within systems relying on jose-php for secure communications.
The operational impact of CVE-2016-5429 is significant for any system utilizing jose-php versions prior to 2.2.1 for implementing JSON Web Token security. Organizations deploying web applications, APIs, or services that depend on this library for authentication and authorization mechanisms face elevated risk of credential compromise and data breaches. The vulnerability affects the core cryptographic operations that ensure data integrity and authentication, making it particularly dangerous for systems handling sensitive information such as user credentials, personal data, or confidential business information. The timing attack vectors can be executed remotely, requiring minimal privileges and potentially allowing attackers to gradually reconstruct valid authentication tokens through repeated measurements.
Mitigation strategies for this vulnerability require immediate remediation through library updates to version 2.2.1 or later, which implements proper constant-time HMAC comparison operations. Security administrators should conduct comprehensive inventory assessments to identify all systems utilizing affected jose-php versions and prioritize patching efforts accordingly. Additional defensive measures include implementing network monitoring to detect anomalous timing patterns that may indicate exploitation attempts, applying rate limiting to authentication endpoints, and considering the deployment of intrusion detection systems capable of identifying timing-based attack patterns. Organizations should also review their cryptographic implementation practices to ensure all HMAC comparisons use constant-time algorithms, as recommended by NIST SP 800-131A and other cryptographic standards that emphasize the importance of preventing timing attacks in security-critical applications.