CVE-2009-3875 in JRE
Summary
by MITRE
The MessageDigest.isEqual function in Java Runtime Environment (JRE) in Sun Java SE in JDK and JRE 5.0 before Update 22, JDK and JRE 6 before Update 17, SDK and JRE 1.3.x before 1.3.1_27, and SDK and JRE 1.4.x before 1.4.2_24 allows remote attackers to spoof HMAC-based digital signatures, and possibly bypass authentication, via unspecified vectors related to "timing attack vulnerabilities," aka Bug Id 6863503.
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Analysis
by VulDB Data Team • 02/26/2025
The vulnerability described in CVE-2009-3875 represents a critical timing attack vulnerability within the Java MessageDigest.isEqual function that affects multiple versions of the Java Runtime Environment. This flaw specifically targets the implementation of cryptographic comparison operations used in HMAC-based digital signature verification processes. The vulnerability arises from the non-constant time execution behavior of the isEqual function, which exposes timing information that can be exploited by remote attackers to determine the validity of cryptographic signatures through side-channel analysis. The issue impacts Sun Java SE versions including JDK and JRE 5.0 before Update 22, JDK and JRE 6 before Update 17, and older SDK and JRE versions 1.3.x before 1.3.1_27 and 1.4.x before 1.4.2_24, making it a widespread concern across the Java ecosystem.
The technical flaw stems from the implementation of the MessageDigest.isEqual function which performs a byte-by-byte comparison of cryptographic values without ensuring constant-time execution. When comparing two hash values, an attacker can measure the time difference required for the comparison operation to complete, as the function typically returns early when it encounters a mismatched byte. This timing variation creates a side-channel attack vector that allows adversaries to progressively determine the correct hash value through statistical analysis and multiple request attempts. The vulnerability directly relates to CWE-203, which describes "Information Exposure Through Discrepancy in Time-Based Operations," and aligns with ATT&CK technique T1212 for "Exploitation for Credential Access" through timing-based information leakage. The implementation fails to provide constant-time comparison operations that are essential for cryptographic security.
The operational impact of this vulnerability extends beyond simple authentication bypasses to encompass broader security implications for systems relying on HMAC-based authentication mechanisms. Attackers can exploit this weakness to forge digital signatures, bypass authentication systems, and potentially gain unauthorized access to protected resources. The vulnerability affects applications that depend on Java's cryptographic libraries for security operations including web applications, enterprise systems, and any software implementing HMAC-based signature verification. The timing attack approach allows for relatively efficient exploitation compared to other side-channel methods, making it particularly dangerous in environments where network traffic analysis is possible. Systems using Java-based authentication protocols, SSL/TLS implementations, and cryptographic signature verification are all at risk when running vulnerable Java versions.
Mitigation strategies for CVE-2009-3875 require immediate patching of affected Java installations to the latest available updates, specifically applying the security patches released by Oracle for the affected Java versions. Organizations should implement comprehensive vulnerability management processes to identify and remediate all systems running vulnerable Java versions. Alternative approaches include implementing constant-time comparison functions in custom cryptographic implementations, though this requires careful code review and testing. Network-level protections such as rate limiting and monitoring for anomalous timing patterns can help detect exploitation attempts, while application-level security controls should be enhanced to include additional authentication factors beyond HMAC-based signatures. The vulnerability serves as a reminder of the critical importance of constant-time cryptographic implementations and proper security testing for all cryptographic operations within software systems.