CVE-2021-39912 in Community Edition
Summary
by MITRE • 11/05/2021
A potential DoS vulnerability was discovered in GitLab CE/EE starting with version 13.7. Using a malformed TIFF images was possible to trigger memory exhaustion.
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Analysis
by VulDB Data Team • 11/09/2021
The vulnerability identified as CVE-2021-39912 represents a denial of service weakness in GitLab Community Edition and Enterprise Edition products that affects versions 13.7 and later. This security flaw manifests through the processing of malformed TIFF image files within the GitLab environment, creating a scenario where malicious actors can exploit the system's image handling mechanisms to consume excessive memory resources. The issue stems from inadequate input validation and sanitization during the TIFF image parsing process, which allows specially crafted image files to trigger unexpected memory allocation patterns within the GitLab application.
The technical exploitation of this vulnerability occurs when GitLab attempts to process or display a malformed TIFF image file, typically through its web interface or file upload mechanisms. The flaw lies in how the application handles TIFF metadata and image data structures, particularly when encountering corrupted or malformed image headers that cause the parsing libraries to allocate excessive memory buffers. This memory exhaustion can occur during various operations including image preview generation, file validation, or even simple file listing operations within GitLab's repository management system. The vulnerability is classified under CWE-400 as an Uncontrolled Resource Consumption weakness, specifically manifesting as a memory exhaustion attack that can render the GitLab instance unresponsive or cause system instability.
The operational impact of CVE-2021-39912 extends beyond simple service disruption to potentially compromise the entire GitLab environment's availability and performance. When exploited, this vulnerability can cause significant memory allocation patterns that may lead to process termination, system slowdowns, or complete service unavailability for legitimate users. The attack vector is particularly concerning because it can be triggered through normal GitLab operations such as repository browsing, file uploads, or merge request creation where image files are processed. This vulnerability directly impacts GitLab's core functionality and can be leveraged by attackers to perform persistent denial of service attacks against GitLab installations, making it a critical concern for organizations relying on GitLab for version control and collaboration services.
Organizations affected by this vulnerability should implement immediate mitigations including updating to patched versions of GitLab where available, implementing file type validation and sanitization measures, and configuring proper resource limits and monitoring for memory consumption. The ATT&CK framework categorizes this as a resource exhaustion technique under the T1499.004 sub-technique, which involves consuming system resources to deny service to legitimate users. Security teams should also consider implementing network-based intrusion detection systems to monitor for suspicious image file processing patterns and establish automated alerting for unusual memory consumption spikes within GitLab processes. Additionally, organizations should conduct regular security assessments of their GitLab installations to identify and remediate similar vulnerabilities in third-party libraries and components that may be susceptible to similar exploitation patterns.