CVE-2021-39932 in Community Edition
Summary
by MITRE • 12/13/2021
An issue has been discovered in GitLab CE/EE affecting all versions starting from 11.0 before 14.3.6, all versions starting from 14.4 before 14.4.4, all versions starting from 14.5 before 14.5.2. Using large payloads, the diff feature could be used to trigger high load time for users reviewing code changes.
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Analysis
by VulDB Data Team • 12/16/2021
The vulnerability identified as CVE-2021-39932 represents a significant performance degradation issue within GitLab's code review functionality that affects multiple version ranges across the platform's community and enterprise editions. This security flaw specifically targets the diff feature that users employ to examine code changes, creating a potential denial of service condition where legitimate users experience substantial delays when reviewing modifications. The vulnerability manifests when attackers or malicious actors submit large payload data through the diff interface, causing the system to consume excessive computational resources during processing. This issue was particularly concerning as it impacted all versions starting from 11.0 up to 14.3.5, as well as versions from 14.4 through 14.4.3 and 14.5 through 14.5.1, indicating a widespread exposure across multiple release streams.
The technical implementation of this vulnerability stems from insufficient input validation and resource management within GitLab's diff processing pipeline. When users attempt to review code changes containing exceptionally large payloads, the system's diff engine processes these inputs without adequate rate limiting or resource consumption controls. This creates a scenario where the computational overhead required to generate and display the diff information becomes disproportionately high, leading to extended processing times that can range from several seconds to minutes depending on the payload size. The underlying flaw can be categorized as a resource exhaustion vulnerability that operates under CWE-400, specifically targeting the system's ability to handle large inputs efficiently. The issue directly impacts the system's availability and user experience, as legitimate developers face significant delays when attempting to perform routine code review activities.
The operational impact of this vulnerability extends beyond simple performance degradation to potentially compromise the entire development workflow within GitLab environments. Teams relying on the platform for continuous integration and code review processes may experience substantial disruptions when encountering large payloads, which could delay release cycles and reduce overall productivity. The vulnerability creates an attack surface that malicious actors can exploit to systematically degrade system performance, making it difficult for legitimate users to access or review code changes. This type of vulnerability aligns with ATT&CK technique T1499.004, which covers network disruption through resource exhaustion, and represents a significant concern for organizations where GitLab serves as a critical infrastructure component for software development operations. The impact is particularly severe in environments where automated systems or CI/CD pipelines might inadvertently trigger these conditions through large code commits or batch operations.
Mitigation strategies for CVE-2021-39932 should focus on implementing comprehensive input validation and resource management controls within the diff processing functionality. Organizations should immediately upgrade to the patched versions 14.3.6, 14.4.4, and 14.5.2 to address the vulnerability at its source. Additionally, administrators should consider implementing rate limiting mechanisms and payload size restrictions for diff operations to prevent excessive resource consumption. The implementation of monitoring and alerting systems can help detect unusual diff processing patterns that might indicate exploitation attempts. Security teams should also review their incident response procedures to ensure they can quickly identify and respond to performance degradation incidents related to code review functionality. Organizations may need to implement temporary workarounds such as restricting diff processing for particularly large files or implementing manual review processes for unusually large commits until full patches are deployed. The vulnerability serves as a reminder of the importance of robust resource management in collaborative development platforms where user-generated content can potentially be used to create system performance issues.