CVE-2026-18252 in GitLab
Summary
by MITRE • 08/26/2026
GitLab has remediated an issue in GitLab EE affecting all versions from 18.9 before 19.1.7, 19.2 before 19.2.5, and 19.3 before 19.3.1 that, under certain conditions, an authenticated user with developer-role permissions could have executed arbitrary commands in a CI context, due to the Claude agent processing configuration from a user-controlled source.
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Analysis
by VulDB Data Team • 08/26/2026
GitLab has addressed a critical security vulnerability affecting its Enterprise Edition across multiple release branches, specifically versions 18.9 prior to 19.1.7, 19.2 prior to 19.2.5, and 19.3 prior to 19.3.1. This flaw stems from the integration of an AI-driven Claude agent within the CI/CD pipeline infrastructure. The vulnerability arises because the configuration parameters for this agent are processed using input derived directly from user-controlled sources without sufficient sanitization or validation mechanisms in place during certain operational conditions.
The core technical deficiency lies in how the system handles inputs provided by users who possess developer-level permissions. In a typical GitLab CI/CD environment, developers can define pipeline configurations that dictate build, test, and deployment steps. When these pipelines invoke the Claude agent for tasks such as code review or automated testing, the agent's configuration is dynamically constructed based on user-provided data. Due to inadequate input validation, an authenticated developer with sufficient privileges could inject malicious payloads into this configuration stream. This allows the attacker to manipulate how the agent processes instructions, effectively bypassing intended security boundaries within the CI context.
The operational impact of this vulnerability is severe, as it enables arbitrary command execution on the infrastructure running the CI jobs. Since GitLab runners often operate with elevated privileges to facilitate complex build and deployment tasks, successful exploitation could allow an attacker to execute system-level commands, access sensitive repository data, or pivot further into the internal network. This represents a significant risk to organizations relying on automated pipelines for their software delivery lifecycle, as it compromises both confidentiality and integrity of the development environment.
From a classification perspective, this vulnerability aligns with CWE-94 Improper Control of Generation of Code Command Injection, specifically where user input influences code generation or execution parameters without proper neutralization. In terms of adversary behavior mapping to MITRE ATT&CK, this exploit vector corresponds to T1059 Command and Scripting Interpreter, as it allows for the execution of arbitrary commands within a managed environment. It also touches upon T1620 Reflective Code Injection if the agent processes code snippets dynamically, though the primary mechanism is command injection via configuration manipulation.
Mitigation strategies require immediate action by upgrading to patched versions across all affected branches: 19.1.7 or later for the 18.9 series, 19.2.5 or later for the 19.2 series, and 19.3.1 or later for the 19.3 series. Organizations should also review their CI/CD pipeline configurations to ensure that no sensitive credentials are stored in variables accessible to lower-privileged users who might interact with AI-assisted features. Implementing strict role-based access control policies is essential, ensuring that only trusted administrators can modify critical agent settings or deploy changes to shared runners. Additionally, enabling audit logs for configuration changes and monitoring for anomalous command execution patterns within CI jobs can help detect potential exploitation attempts in real-time.