CVE-2023-45316 is a high-severity vulnerability affecting Mattermost, an open-source collaboration and messaging platform widely used for team communication. The vulnerability arises from improper validation of a relative path passed as a telemetry run ID in the endpoint /plugins/playbooks/api/v0/telemetry/run/<telem_run_id>. Specifically, Mattermost fails to properly validate this input, allowing an attacker to craft a path traversal payload that redirects the request to a different internal endpoint. This manipulation enables a Cross-Site Request Forgery (CSRF) attack, classified under CWE-352. In a CSRF attack, an authenticated user can be tricked into submitting unauthorized requests to the application, potentially leading to unauthorized actions being performed with the victim's privileges. The CVSS 3.1 base score of 7.3 reflects the vulnerability's characteristics: it is remotely exploitable over the network (AV:N), requires low attack complexity (AC:L), but does require some privileges (PR:L) and user interaction (UI:R). The impact is significant, with no confidentiality impact but high integrity and availability impacts, meaning attackers can alter or disrupt system operations. Although no known exploits are currently reported in the wild, the vulnerability's presence in Mattermost's telemetry plugin endpoint presents a risk for organizations using this platform, especially if they have users with elevated privileges. The lack of patch links suggests that a fix may not yet be publicly available or is pending release.

For European organizations, the impact of this vulnerability can be substantial, particularly for those relying on Mattermost for internal communications and workflow automation. Successful exploitation could allow attackers to perform unauthorized actions such as modifying playbook executions, disrupting telemetry data collection, or interfering with operational processes managed through Mattermost plugins. This could lead to operational downtime, loss of data integrity, and potential disruption of critical business functions. Since Mattermost is often used in sectors like finance, healthcare, and government within Europe, the risk extends to sensitive environments where integrity and availability are paramount. Additionally, the requirement for some level of user privilege and interaction means targeted phishing or social engineering campaigns could be used to exploit this vulnerability, increasing the risk to organizations with less mature security awareness programs. The absence of confidentiality impact reduces the risk of data leakage but does not mitigate the threat to system integrity and availability, which can have cascading effects on business continuity and regulatory compliance, especially under GDPR and other European data protection laws.

European organizations should implement several specific mitigations beyond generic advice: 1) Immediately audit Mattermost deployments to identify usage of the vulnerable telemetry plugin endpoint and restrict access to it via network segmentation or firewall rules to trusted users only. 2) Enforce strict Content Security Policies (CSP) and SameSite cookie attributes to reduce the risk of CSRF exploitation. 3) Implement multi-factor authentication (MFA) for all Mattermost users, especially those with elevated privileges, to reduce the risk of session hijacking or unauthorized actions. 4) Educate users on phishing and social engineering risks to minimize the chance of user interaction leading to exploitation. 5) Monitor Mattermost logs for unusual activity related to the telemetry endpoint and suspicious requests containing path traversal patterns. 6) Engage with Mattermost support or community channels to obtain patches or updates addressing this vulnerability as soon as they become available and prioritize timely deployment. 7) Consider temporary disabling or removing the vulnerable plugin if it is not critical to operations until a patch is applied.