CVE-2022-1100 in Community Edition
Summary
by MITRE • 04/05/2022
A potential DOS vulnerability was discovered in GitLab CE/EE affecting all versions from 13.1 prior to 14.7.7, 14.8.0 prior to 14.8.5, and 14.9.0 prior to 14.9.2. The api to update an asset as a link from a release had a regex check which caused exponential number of backtracks for certain user supplied values resulting in high CPU usage.
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Analysis
by VulDB Data Team • 04/06/2022
This vulnerability represents a classic denial of service attack vector through regex backtracking optimization issues that can be exploited to consume excessive computational resources. The flaw exists within GitLab's release asset management functionality where the system validates user-provided values through a regular expression pattern. When maliciously crafted input is processed through this validation mechanism, the regex engine enters into a state of exponential backtracking that dramatically increases CPU consumption and can lead to complete system unresponsiveness. This vulnerability specifically affects GitLab Community and Enterprise editions across multiple version ranges, indicating it was a widespread issue that required patching across different release branches. The attack surface is particularly concerning as it involves user-controlled input that can be submitted through the API endpoint designed for updating release assets that are links to external resources.
The technical implementation of this vulnerability stems from the regex pattern used for validating release asset links, which contains constructs that are vulnerable to catastrophic backtracking when processing certain input strings. This behavior is classified under CWE-1321 as "Improper Restriction of Regular Expression Complexity" and aligns with the broader category of regex denial of service vulnerabilities that have been documented in numerous security frameworks and standards. The regex engine performs an exponential number of backtracking operations when encountering specific character sequences in user input, causing the system to spend disproportionate amounts of CPU time processing what should be simple validation operations. This type of vulnerability is particularly dangerous in web applications where input validation occurs frequently and can be triggered by any user with appropriate access permissions, making it a significant threat to system availability and service integrity.
The operational impact of this vulnerability extends beyond simple resource exhaustion to potentially disrupt critical development workflows and continuous integration processes that rely on GitLab's release management features. Attackers can exploit this vulnerability by submitting carefully crafted asset link values that trigger the regex backtracking behavior, leading to sustained high CPU usage that can affect other system processes and potentially cause cascading failures. This vulnerability is particularly concerning for organizations that use GitLab extensively for software development and deployment, as it can be exploited to disrupt development cycles and cause service degradation. The attack can be executed with minimal privileges, making it accessible to users who have basic access to release management functionality. From an ATT&CK framework perspective, this vulnerability maps to T1499.004 "Endpoint Denial of Service" and represents a method of resource exhaustion that can be used to degrade service availability.
The mitigation strategy for this vulnerability involves applying the appropriate patches released by GitLab for the affected versions, which typically include regex pattern modifications or validation logic improvements that prevent catastrophic backtracking scenarios. Organizations should prioritize patching all affected GitLab installations to prevent exploitation, as the vulnerability can be leveraged to cause significant operational disruption. Additionally, implementing input validation controls and rate limiting on API endpoints can provide additional defense-in-depth measures to reduce the impact of potential exploitation attempts. The fix typically involves either rewriting the vulnerable regex patterns to eliminate backtracking issues or implementing alternative validation approaches that do not rely on regex engines with known performance limitations. Security teams should monitor their GitLab installations for any signs of exploitation attempts and maintain updated threat intelligence regarding similar vulnerabilities in related software components.