CVE-2025-3230 is a medium-severity vulnerability affecting multiple versions of the Mattermost collaboration platform, specifically versions 9.11.0 through 9.11.12, 10.5.0 through 10.5.3, 10.6.0 through 10.6.2, and 10.7.0 through 10.7.x. The vulnerability arises from an incorrect implementation of the authentication algorithm (CWE-303), where personal access tokens (PATs) are not properly invalidated when a user account is deactivated. This flaw allows deactivated users to retain full system access by continuing to use previously issued tokens, bypassing the intended access revocation mechanisms. The vulnerability has a CVSS 3.1 base score of 5.4, indicating a medium severity level. The vector indicates that the attack can be performed remotely (AV:N) with low attack complexity (AC:L), requiring privileges (PR:L) but no user interaction (UI:N). The impact affects confidentiality and integrity but not availability. No known exploits are currently reported in the wild. The core technical issue is that the token validation logic fails to check the active status of the user account associated with the token, allowing unauthorized persistence of access rights post-deactivation. This undermines the security model of user lifecycle management and token revocation in Mattermost, potentially enabling unauthorized data access or manipulation by former users or attackers who have compromised such tokens.

For European organizations using Mattermost, this vulnerability poses a significant risk to internal communication confidentiality and data integrity. Since Mattermost is widely used for team collaboration, unauthorized access via lingering personal access tokens could lead to exposure of sensitive corporate information, intellectual property, or personal data protected under GDPR. The failure to revoke access upon user deactivation means that former employees, contractors, or compromised accounts could maintain persistent access, increasing insider threat risks and complicating incident response. This could result in data breaches, regulatory non-compliance penalties, and reputational damage. The medium CVSS score reflects that while exploitation requires some level of privilege, the lack of user interaction and remote exploitability make it a practical threat in environments where token management policies are not strictly enforced. The impact is particularly critical in sectors with stringent data protection requirements such as finance, healthcare, and government agencies within Europe.

European organizations should immediately audit their Mattermost deployments to identify affected versions and upgrade to patched versions once available. In the absence of patches, organizations should implement compensating controls such as: 1) Manually revoking all personal access tokens associated with deactivated users through administrative interfaces or API calls. 2) Enforcing short token lifetimes and rotating tokens frequently to limit the window of exposure. 3) Enhancing monitoring and alerting for unusual token usage patterns, especially from deactivated accounts. 4) Implementing strict user deactivation workflows that include token revocation as a mandatory step. 5) Restricting token issuance privileges to trusted administrators and limiting token scopes to minimize potential damage. 6) Employing network-level access controls and multi-factor authentication to reduce the risk of token misuse. Additionally, organizations should review their incident response plans to include scenarios involving token misuse by deactivated users.