CVE-2017-0918 in Community Edition
Summary
by MITRE
Gitlab Community Edition version 10.3 is vulnerable to a path traversal issue in the GitLab CI runner component resulting in remote code execution.
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Analysis
by VulDB Data Team • 01/15/2020
The vulnerability identified as CVE-2017-0918 affects GitLab Community Edition version 10.3 and represents a critical path traversal flaw within the GitLab CI runner component. This issue arises from insufficient input validation and improper handling of file paths during the execution of CI jobs, creating a dangerous attack vector that can be exploited by remote adversaries. The vulnerability stems from the runner's failure to properly sanitize user-supplied input when processing job artifacts and build files, allowing attackers to manipulate file system access through carefully crafted malicious inputs.
The technical implementation of this vulnerability involves the GitLab CI runner's handling of relative paths and symbolic links during artifact processing. When a CI job is executed, the runner processes build artifacts and temporary files without adequate validation of the file paths being referenced. This weakness enables attackers to craft malicious job configurations that can traverse directories outside the intended execution context. The flaw specifically manifests when the runner processes files with specially crafted names or paths that exploit directory traversal sequences, allowing unauthorized access to the file system. This type of vulnerability is classified as CWE-22 Path Traversal, which is a well-documented weakness in software systems that fail to properly validate or sanitize file path inputs.
The operational impact of this vulnerability extends beyond simple unauthorized file access, as it provides a complete remote code execution capability to attackers who can leverage the path traversal to inject malicious code into the build environment. An attacker who gains access to a GitLab instance with CI capabilities can exploit this vulnerability to execute arbitrary commands on the runner system, potentially leading to full system compromise. This threat is particularly severe because GitLab CI runners often operate with elevated privileges and may have access to sensitive repositories, credentials, and deployment targets. The vulnerability can be exploited through various attack vectors including malicious CI job definitions, manipulated build artifacts, or compromised project configurations that are processed by the vulnerable runner component.
Organizations utilizing GitLab Community Edition 10.3 should implement immediate mitigations to protect against exploitation of this vulnerability. The primary recommended action is to upgrade to GitLab version 10.4 or later, where the path traversal issue has been addressed through proper input validation and sanitization of file paths within the CI runner component. Additional protective measures include implementing network segmentation to limit access to CI runner systems, enforcing strict access controls for project configurations, and monitoring CI job execution logs for suspicious activity patterns. Security teams should also consider implementing runtime protections such as file system access controls, process monitoring, and anomaly detection systems that can identify potential exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and execution through CI/CD systems, making it particularly dangerous in environments where GitLab is integrated with other security tools and automated deployment pipelines. The vulnerability demonstrates the critical importance of input validation in CI/CD environments and highlights the need for comprehensive security testing of build and deployment automation systems.