CVE-2014-8242 in librsync
Summary
by MITRE
librsync before 1.0.0 uses a truncated MD4 checksum to match blocks, which makes it easier for remote attackers to modify transmitted data via a birthday attack.
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Analysis
by VulDB Data Team • 06/25/2022
The vulnerability identified as CVE-2014-8242 affects librsync versions prior to 1.0.0 and stems from the use of a truncated MD4 checksum algorithm for block matching during data synchronization operations. This cryptographic weakness fundamentally undermines the integrity verification mechanism that librsync employs to ensure data consistency between source and target systems. The implementation relies on MD4, a hash function that was already considered cryptographically weak by the time this vulnerability was discovered, particularly when used in truncated form for block identification purposes. The truncated nature of the checksum means that only a portion of the full MD4 digest is used for matching blocks, significantly reducing the entropy and making collision attacks more feasible.
The operational impact of this vulnerability manifests through a birthday attack vector that allows remote attackers to manipulate transmitted data without detection. In cryptographic terms, a birthday attack exploits the mathematics of probability to find collisions in hash functions, where two different inputs produce the same output hash value. With truncated MD4 checksums, the reduced output size creates a smaller search space for attackers to find matching block patterns, effectively lowering the computational requirements needed to craft malicious data modifications. This vulnerability is particularly concerning in networked environments where librsync is used for file synchronization, backup operations, or incremental data transfer protocols, as it creates opportunities for data integrity compromise without requiring extensive computational resources or advanced cryptographic knowledge.
The security implications extend beyond simple data corruption, as this weakness can enable more sophisticated attack scenarios including man-in-the-middle operations, data injection attacks, and potential privilege escalation when librsync is integrated into larger security systems. According to the CWE catalog, this vulnerability maps to CWE-327, which addresses the use of weak cryptographic algorithms, and CWE-310, which covers cryptographic issues related to key management and algorithm selection. The attack surface is further expanded when considering ATT&CK framework mappings, particularly under techniques related to credential access and defense evasion, as compromised data integrity can lead to downstream security issues that attackers might exploit to gain unauthorized access or hide malicious activities within synchronized data streams.
Mitigation strategies for CVE-2014-8242 require immediate upgrading to librsync version 1.0.0 or later, which addresses the truncated checksum issue by implementing proper cryptographic hashing mechanisms. Organizations should conduct comprehensive inventory assessments to identify all systems utilizing vulnerable librsync versions and prioritize remediation efforts based on risk exposure. Additionally, network monitoring should be enhanced to detect anomalous data synchronization patterns that might indicate successful exploitation attempts. Security teams should also consider implementing additional integrity verification mechanisms beyond what librsync provides, such as using digital signatures or implementing multi-layered checksum validation to provide defense-in-depth against potential exploitation of similar cryptographic weaknesses in other components of the data synchronization pipeline.