CVE-2023-2788 in Server
Summary
by MITRE • 06/16/2023
Mattermost fails to check if an admin user account active after an oauth2 flow is started, allowing an attacker with admin privileges to retain persistent access to Mattermost by obtaining an oauth2 access token while the attacker's account is deactivated.
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Analysis
by VulDB Data Team • 07/14/2023
The vulnerability described in CVE-2023-2788 represents a critical authorization flaw within the Mattermost collaboration platform that undermines the security of administrative accounts during OAuth2 authentication flows. This issue arises from a fundamental failure in the platform's session management and account validation mechanisms, specifically during the OAuth2 authentication process where the system does not properly verify the active status of administrator accounts. The flaw exists in the authentication flow logic where the system grants access tokens to accounts that may have been deactivated or suspended, creating a persistent backdoor for attackers who have already gained administrative privileges.
The technical implementation of this vulnerability stems from improper account state validation during OAuth2 token issuance. When an administrator account is deactivated, the system should invalidate any existing sessions or tokens associated with that account, but the Mattermost platform fails to perform this critical validation step. This design flaw allows an attacker who has already compromised administrative credentials to maintain access even after their account has been disabled by legitimate administrators. The vulnerability specifically affects the OAuth2 authentication flow where the platform issues access tokens without revalidating the account's active status, creating a window of opportunity for persistent unauthorized access.
From an operational security perspective, this vulnerability poses significant risks to organizations relying on Mattermost for collaboration and communication. The impact extends beyond simple unauthorized access, as it enables attackers to maintain long-term presence within the platform without detection, potentially leading to data exfiltration, privilege escalation, and insider threat scenarios. The vulnerability directly relates to CWE-613, which addresses insufficient session management, and can be mapped to ATT&CK technique T1078.004 for valid accounts, as it allows attackers to maintain access through compromised administrative credentials. Organizations using Mattermost may experience continuous security exposure where legitimate administrators cannot effectively revoke access from compromised accounts.
The mitigation strategy for this vulnerability requires immediate implementation of account state validation during OAuth2 token issuance processes. Organizations should ensure that all authentication flows validate the active status of accounts before issuing access tokens, particularly for administrative accounts. The platform should enforce re-authentication requirements when account status changes, implement proper token revocation mechanisms, and establish monitoring for suspicious authentication patterns. Security teams should also consider implementing additional controls such as account lockout mechanisms, multi-factor authentication for administrative accounts, and regular security audits of authentication flows to prevent similar issues from occurring in other components of the platform.