CVE-2024-52521 in Server
Summary
by MITRE • 11/15/2024
Nextcloud Server is a self hosted personal cloud system. MD5 hashes were used to check background jobs for their uniqueness. This increased the chances of a background job with arguments falsely being identified as already existing and not be queued for execution. By changing the Hash to SHA256 the probability was heavily decreased. It is recommended that the Nextcloud Server is upgraded to 28.0.10, 29.0.7 or 30.0.0.
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Analysis
by VulDB Data Team • 02/26/2025
The vulnerability identified as CVE-2024-52521 affects Nextcloud Server, a widely deployed self-hosted personal cloud system that enables users to store and synchronize files across multiple devices. This security flaw resides in the background job processing mechanism of the platform, specifically in how the system validates job uniqueness through cryptographic hashing. The implementation utilizes MD5 hashes for checking whether background jobs with identical arguments are already queued for execution, creating a fundamental weakness in the system's job management architecture that directly impacts operational reliability and security posture.
The technical flaw stems from the inherent cryptographic weaknesses of MD5 algorithm, which has been extensively documented as vulnerable to collision attacks since the early 2000s. When Nextcloud Server employs MD5 to generate hashes for background job identification, it creates a scenario where malicious actors or system anomalies can potentially generate different job arguments that produce identical MD5 hash values. This collision probability, while mathematically small for random inputs, becomes significantly more likely when considering the specific patterns and argument structures commonly used in background job processing. The vulnerability manifests when the system incorrectly identifies a new job as a duplicate due to hash collision, resulting in legitimate background processes being suppressed from execution.
The operational impact of this vulnerability extends beyond simple job queuing failures, as it can compromise the integrity of automated system maintenance tasks and user workflows that depend on background processing. When background jobs fail to execute properly due to false duplicate detection, it can lead to incomplete data synchronization, failed automated backups, or disrupted system maintenance operations that may go unnoticed for extended periods. This represents a significant reliability issue that affects the core functionality of Nextcloud Server, particularly in environments where automated processes are critical for system operation. The vulnerability essentially creates a race condition where legitimate job execution is blocked by cryptographic hash collisions, potentially leading to cascading failures in system maintenance and user experience degradation.
The remediation strategy involves upgrading Nextcloud Server to version 28.0.10, 29.0.7, or 30.0.0, where the implementation has been updated to utilize SHA256 hashing instead of MD5 for background job uniqueness verification. This change addresses the fundamental cryptographic weakness by employing a more robust hashing algorithm that significantly reduces the probability of collisions. The SHA256 algorithm provides a 256-bit output that offers substantially better resistance to collision attacks compared to MD5's 128-bit output, making the likelihood of accidental hash collisions negligible in practical deployment scenarios. This upgrade represents a direct alignment with security best practices and industry standards that recommend moving away from deprecated cryptographic algorithms. Organizations should prioritize this upgrade as part of their vulnerability management strategy, particularly given the potential for these collisions to silently disrupt critical background operations. The fix demonstrates proper security engineering practices by transitioning from a known weak cryptographic primitive to a well-established secure alternative, following the principle of least privilege and robust system design that aligns with both CWE guidelines for cryptographic implementation failures and ATT&CK techniques related to system service manipulation and process injection.