CVE-2026-3855 in GitLab
Summary
by MITRE • 09/16/2026
GitLab has remediated an issue in GitLab CE/EE affecting all versions from 18.2.7 before 19.1.8, 19.2 before 19.2.6, and 19.3 before 19.3.2 that under certain conditions could have allowed an authenticated user with project-level permissions to access restricted file contents on the server or cause denial of service due to improper validation of parameters in the Terraform state upload functionality.
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Analysis
by VulDB Data Team • 09/16/2026
GitLab has addressed a critical security vulnerability within its Community Edition and Enterprise Edition platforms, impacting version ranges from 18.2.7 up to but not including 19.1.8, as well as versions 19.2 prior to 19.2.6 and 19.3 prior to 19.3.2. This flaw stems from improper validation of parameters within the Terraform state upload functionality, a feature used by DevOps teams to manage infrastructure-as-code configurations. The vulnerability allows an authenticated user who possesses project-level permissions to exploit this weakness under specific conditions, leading to either unauthorized access to restricted file contents on the server or causing a denial of service condition that disrupts normal operations for other users and services relying on the platform.
The technical root cause lies in insufficient input sanitization and validation logic within the component responsible for handling Terraform state files. When an authenticated user uploads a state file, the system fails to adequately verify certain parameters associated with the upload process. This lack of rigorous checks enables malicious actors to craft requests that bypass expected access controls or trigger resource exhaustion mechanisms inherent in how the server processes these specific inputs. By manipulating these parameters, an attacker can potentially traverse directory structures or exploit parsing errors to read files that should remain inaccessible based on their assigned role and project permissions.
From a security classification perspective, this vulnerability aligns with CWE-20 Improper Input Validation, as the core issue is the failure to properly sanitize user-supplied data before processing it within the application logic. Furthermore, the potential for unauthorized access to restricted files corresponds closely to CWE-284 Improper Access Control, indicating a breakdown in enforcing least privilege principles during file operations. In terms of offensive security frameworks such as MITRE ATT&CK, this behavior is consistent with techniques involving T1083 File and Directory Discovery or potentially T1567 Exfiltration Over Web Service if the attacker uses the upload mechanism to exfiltrate sensitive data disguised as state files. The denial of service aspect relates to resource manipulation that can degrade availability, a key component of the CIA triad in information security.
The operational impact of this vulnerability is significant for organizations relying on GitLab for their CI/CD pipelines and infrastructure management workflows. An attacker with even basic project-level access could escalate privileges by reading sensitive configuration files, secrets, or internal server data that are not intended to be exposed at the project level. This exposure can lead to further compromise of downstream systems if credentials or API keys stored in Terraform state files are harvested. Additionally, the denial of service capability means that malicious actors could intentionally crash services or consume excessive system resources by submitting malformed payloads repeatedly, thereby disrupting development workflows and potentially causing financial loss due to downtime.
To mitigate this risk, organizations must immediately upgrade their GitLab instances to versions 19.1.8 or later for the 19.1 branch, 19.2.6 or later for the 19.2 branch, and 19.3.2 or later for the 19.3 branch. Until upgrades are performed, administrators should review access controls to ensure that only trusted users have project-level permissions capable of interacting with Terraform state uploads. Implementing strict network segmentation and monitoring upload logs for anomalous patterns can also help detect exploitation attempts in real-time. Regular security audits and adherence to the principle of least privilege across all user roles are essential practices to minimize the attack surface associated with such vulnerabilities.