CVE-2023-5356 in Community Edition
Summary
by MITRE • 01/12/2024
Incorrect authorization checks in GitLab CE/EE from all versions starting from 8.13 before 16.5.6, all versions starting from 16.6 before 16.6.4, all versions starting from 16.7 before 16.7.2, allows a user to abuse slack/mattermost integrations to execute slash commands as another user.
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Analysis
by VulDB Data Team • 11/20/2025
The vulnerability identified as CVE-2023-5356 represents a critical authorization flaw within GitLab Community Edition and Enterprise Edition platforms that affects multiple version ranges. This issue stems from insufficient validation of user permissions when processing slash commands through third-party integration services such as Slack and Mattermost. The flaw allows malicious or unauthorized users to exploit the integration mechanisms to execute commands on behalf of other users, effectively bypassing the intended access controls and privilege boundaries. Such a vulnerability directly undermines the principle of least privilege and can lead to unauthorized actions within the integrated development and collaboration environment.
The technical root cause of this vulnerability lies in the improper validation of command origins and user identities within the GitLab integration processing pipeline. When users configure Slack or Mattermost integrations with GitLab projects, the system should verify that commands issued through these channels originate from authorized users with appropriate permissions within the project context. However, the flawed implementation fails to adequately authenticate or authorize the execution context of slash commands, allowing an attacker to manipulate the command execution flow. This authorization bypass occurs specifically during the processing of commands that would normally be restricted to project administrators or members with specific roles, creating a pathway for privilege escalation through integration abuse.
The operational impact of CVE-2023-5356 extends beyond simple unauthorized access, as it enables attackers to potentially execute destructive or disruptive commands within integrated environments. Attackers could leverage this vulnerability to trigger automated workflows, modify project settings, access sensitive information, or manipulate continuous integration pipelines through commands that should only be executable by authorized personnel. The implications are particularly severe in enterprise environments where GitLab serves as a central collaboration and development platform, as successful exploitation could lead to data compromise, service disruption, or unauthorized code deployments. This vulnerability particularly affects organizations that heavily rely on integration-based automation and collaborative workflows.
Organizations should immediately apply the relevant security patches to address this vulnerability, with the specific versions requiring updates being 16.5.6, 16.6.4, and 16.7.2 respectively. System administrators should conduct comprehensive audits of all Slack and Mattermost integrations within their GitLab environments to identify and disable any unnecessary or untrusted integrations. Additional mitigations include implementing stricter access controls for integration endpoints, monitoring command execution logs for suspicious activities, and establishing network-level restrictions to limit external integration access. From a cybersecurity perspective, this vulnerability aligns with CWE-285, which addresses improper authorization issues, and could be categorized under ATT&CK technique T1078 for valid accounts and T1566 for social engineering through integration abuse. Organizations should also consider implementing multi-factor authentication for integration endpoints and establishing incident response procedures specifically targeting unauthorized command execution scenarios.