Overview
CVE-2025-13870 describes a low-severity vulnerability affecting Mattermost Boards. Specifically, versions 10.11.x up to and including 10.11.4, and versions 10.5.x up to and including 10.5.12, are impacted. The vulnerability stems from a failure to properly validate user permissions when accessing files and subscribing to blocks within the Boards feature. This allows an authenticated user to potentially access board files belonging to other users and subscribe to blocks from boards to which they should not have access.
Technical Details
The root cause lies in insufficient authorization checks within the Boards functionality. When a user attempts to access a file or subscribe to a block in a board, the application fails to reliably verify if the user has the necessary permissions for that specific resource. This oversight leads to the possibility of an authenticated user bypassing access controls and gaining unauthorized access to data they should not be able to see or modify. The vulnerability manifests in the following ways:
- Unauthorized File Access: A user can potentially access files associated with boards they are not explicitly granted access to.
- Unauthorized Block Subscription: A user can subscribe to updates and events from blocks within boards they do not have access to, effectively gaining visibility into activity within those boards.
CVSS Analysis
The Common Vulnerability Scoring System (CVSS) assigns CVE-2025-13870 a score of 3.1, indicating a LOW severity. This score reflects the following characteristics:
- Attack Vector (AV): Network (N) – The vulnerability can be exploited over the network.
- Attack Complexity (AC): High (H) – Exploitation requires specialized conditions and expertise.
- Privileges Required (PR): Low (L) – An attacker needs only low-level privileges (an authenticated account) to exploit the vulnerability.
- User Interaction (UI): None (N) – No user interaction is required to trigger the vulnerability.
- Scope (S): Unchanged (U) – An exploited vulnerability can only affect resources managed by the same security authority.
- Confidentiality Impact (C): Low (L) – There is limited disclosure of information.
- Integrity Impact (I): None (N) – There is no impact to data integrity.
- Availability Impact (A): None (N) – There is no impact to system availability.
Although the CVSS score is low, the potential for data leakage and unauthorized monitoring warrants prompt attention and remediation.
Possible Impact
While the severity is low, the potential impact of CVE-2025-13870 should not be ignored. The vulnerability could lead to:
- Data Leakage: Sensitive information stored in board files could be exposed to unauthorized users.
- Unauthorized Monitoring: Attackers could monitor activity within boards they should not have access to, potentially gaining insights into ongoing projects or discussions.
- Internal Reconnaissance: The vulnerability could be used as a stepping stone for more sophisticated attacks by providing attackers with a better understanding of the organization’s internal workings.
Mitigation or Patch Steps
To address CVE-2025-13870, it is highly recommended to upgrade your Mattermost instance to a patched version. Refer to the Mattermost security updates page for the latest information and instructions:
- Upgrade to a version later than 10.11.4 if you are using the 10.11.x branch.
- Upgrade to a version later than 10.5.12 if you are using the 10.5.x branch.
Always follow the official Mattermost upgrade instructions to ensure a smooth and secure update process. Regularly updating your Mattermost instance is crucial for maintaining a secure environment.
