CVE-2024-29215 in Mattermost
Summary
by MITRE • 05/26/2024
Mattermost versions 9.5.x <= 9.5.3, 9.7.x <= 9.7.1, 9.6.x <= 9.6.1, 8.1.x <= 8.1.12 fail to enforce proper access control which allows a user to run a slash command in a channel they are not a member of via linking a playbook run to that channel and running a slash command as a playbook task command.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 05/26/2024
This vulnerability exists in Mattermost server versions across multiple release branches including 8.1.x up to 8.1.12, 9.6.x up to 9.6.1, 9.7.x up to 9.7.1, and 9.5.x up to 9.5.3. The flaw represents a critical access control bypass that undermines the platform's core security model. The vulnerability stems from insufficient validation of user permissions when executing slash commands through playbook automation workflows, allowing unauthorized users to leverage playbook run functionality to execute commands in channels they do not belong to. This represents a direct violation of the principle of least privilege that should govern all collaborative platforms and aligns with CWE-285: Improper Authorization, which specifically addresses insufficient access control mechanisms.
The technical exploitation occurs through a sophisticated attack chain involving playbook automation features within Mattermost's workflow system. An attacker with access to a playbook can link it to a target channel they are not a member of and then schedule or execute a playbook run that includes slash command execution as a task. The system fails to validate whether the executing user has proper channel membership or permissions before allowing the slash command to execute against the target channel. This vulnerability operates at the intersection of playbook automation and channel access control, creating a path for privilege escalation through legitimate automation features. The flaw specifically affects the slash command execution mechanism within automated playbook workflows, bypassing normal channel membership checks that should prevent unauthorized access to channel-specific functionality.
The operational impact of this vulnerability is significant as it enables persistent unauthorized access to sensitive channels and their contents. Attackers can execute arbitrary slash commands in channels they do not own or have access to, potentially leading to data exfiltration, message manipulation, or disruption of channel operations. This vulnerability undermines the integrity of Mattermost's collaboration environment and could be exploited to gain insights into private discussions, manipulate channel content, or even execute commands that might have broader system implications. The attack vector is particularly concerning because it leverages legitimate automation features that administrators typically trust and enable for productivity purposes. Organizations using Mattermost for sensitive communications or compliance-critical environments face heightened risk of unauthorized access and potential data breaches.
The vulnerability directly relates to ATT&CK technique T1078.004: Valid Accounts - Cloud Accounts, as it allows unauthorized users to effectively operate under the guise of legitimate playbook automation. Organizations should implement immediate mitigations including restricting playbook automation permissions, enforcing stricter channel membership validation, and monitoring for unusual playbook execution patterns. The recommended approach involves patching to the latest stable versions where access controls have been properly enforced, implementing additional monitoring of playbook run activities, and reviewing user permissions for playbook creation and execution. Organizations should also consider implementing network-level controls and access reviews to prevent unauthorized playbook creation that could lead to similar vulnerabilities. This vulnerability highlights the importance of comprehensive access control validation in automated systems and demonstrates how seemingly legitimate features can become security risks when proper authorization checks are missing.