CVE-2026-2462 in Mattermost
Summary
by MITRE • 03/16/2026
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to restrict plugin installation on CI test instances with default admin credentials which allows an unauthenticated attacker to achieve remote code execution and exfiltrate sensitive configuration data including AWS and SMTP credentials via uploading a malicious plugin after changing the import directory. Mattermost Advisory ID: MMSA-2025-00528
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Analysis
by VulDB Data Team • 03/20/2026
This vulnerability exists in Mattermost server versions 11.3.0 and earlier, 11.2.2 and earlier, and 10.11.10 and earlier, representing a critical security flaw that enables unauthenticated remote code execution through improper plugin installation restrictions. The flaw specifically affects CI test instances where default administrative credentials remain unchanged, creating an exploitable condition that allows attackers to upload malicious plugins and subsequently execute arbitrary code on the target system. The vulnerability stems from inadequate access controls during the plugin installation process, which should normally require authentication and proper authorization but fails to enforce these restrictions in development and testing environments.
The technical exploitation pathway begins with an attacker identifying a vulnerable Mattermost instance running in a CI environment with default credentials still active. Once access is gained, the attacker can upload a malicious plugin that, when installed, executes code with the privileges of the Mattermost service account. This privilege escalation allows the attacker to modify the plugin import directory and subsequently access sensitive configuration data including AWS credentials, SMTP authentication details, and other potentially sensitive information stored within the Mattermost configuration. The vulnerability is particularly concerning because it leverages the default administrative credentials that are often left unchanged in development and testing environments, making it easily exploitable in poorly configured systems.
The operational impact of this vulnerability extends beyond simple remote code execution to include complete system compromise and data exfiltration. Attackers can leverage this vulnerability to gain persistent access to the Mattermost server, potentially using it as a pivot point for further attacks within the network infrastructure. The exposure of AWS and SMTP credentials represents a significant risk as these credentials can be used to access cloud resources and send emails on behalf of the organization, potentially leading to data breaches, service disruption, and financial loss. Additionally, the vulnerability affects the integrity and confidentiality of all data stored within Mattermost, including chat messages, files, and user information, making it a severe threat to organizational security.
Mitigation strategies should focus on immediate credential management and access control enforcement. Organizations must ensure that default administrative credentials are changed immediately upon installation and that strong, unique passwords are implemented across all Mattermost instances. The plugin installation process should be restricted to authenticated users with appropriate privileges, and automated systems should enforce access controls even in CI environments. Network segmentation and monitoring should be implemented to detect unauthorized plugin uploads and suspicious activities. Regular security audits and vulnerability assessments should be conducted to identify and remediate similar issues in other software components. This vulnerability aligns with CWE-285 (Improper Authorization) and CWE-749 (Exposed Dangerous Method or Function) and maps to ATT&CK techniques including T1059 (Command and Scripting Interpreter) and T1566 (Phishing) for initial access. Organizations should also implement principle of least privilege for plugin management and establish secure development practices that prevent default credentials from being deployed in production environments.