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Mattermost — Vulnerabilities & Security Advisories 504

Browse all 504 CVE security advisories affecting Mattermost. AI-powered Chinese analysis, POCs, and references for each vulnerability.

Mattermost is an open-source, self-hosted messaging platform designed primarily for secure team communication and collaboration within enterprise environments. With 382 recorded Common Vulnerabilities and Exposures (CVEs), the software has historically been susceptible to critical security flaws, including remote code execution, cross-site scripting, and privilege escalation vulnerabilities. These issues often stem from improper input validation or insufficient access controls within its web interface and API layers. While the platform emphasizes data sovereignty through self-hosting, its extensive vulnerability history highlights the risks associated with complex, feature-rich applications. Security incidents have occasionally involved unauthorized data access or service disruption, underscoring the necessity for rigorous patch management and configuration hardening. Organizations deploying this solution must prioritize regular updates and continuous monitoring to mitigate the inherent risks associated with its large attack surface and frequent exposure to newly discovered exploits.

Found 472 results / 504 Clear Filters
CVE ID Title CVSS Severity Published
CVE-2026-18799 Mattermost Server fails to restrict Slack import account binding, allowing team admins to forge posts as existing users — Mattermost CWE-862 4.3 Medium 2026-10-16
CVE-2026-16251 Mattermost local image proxy allows server memory exhaustion via unbounded image response buffering — Mattermost CWE-770 6.5 Medium 2026-10-16
CVE-2026-18256 Private team metadata disclosure via the team search API — Mattermost CWE-863 4.3 Medium 2026-10-16
CVE-2026-18223 Mattermost invitation tokens not bound to invited email address allowing unauthorized team and private channel access — Mattermost CWE-863 5.0 Medium 2026-10-16
CVE-2026-19076 Mattermost fails to reject OAuth application sessions in account type switch, allowing account takeover via bearer token — Mattermost CWE-863 4.4 Medium 2026-10-16
CVE-2026-18560 Improper order of authorisations in Mattermost GetFile API leads to an authenticated user to determine a post’s quarantined status — Mattermost CWE-203 4.3 Medium 2026-10-16
CVE-2026-16453 Mattermost SAML RelayState forgery allows unauthorized team membership — Mattermost CWE-472 7.1 High 2026-10-16
CVE-2026-19600 Mattermost logs plaintext authentication tokens in debug-level server logs on failed auth attempts — Mattermost CWE-532 4.5 Medium 2026-10-16
CVE-2026-19621 Mattermost leaks interactive-message integration secrets to non-admin users via post-deletion events and thread reads — Mattermost CWE-200 6.5 Medium 2026-10-16
CVE-2026-19603 Private channel ID disclosure via user status endpoints — Mattermost CWE-201 4.3 Medium 2026-10-16
CVE-2026-18795 Missing server side validation allowed user to quarantine a DM and GM post — Mattermost CWE-862 6.4 Medium 2026-10-16
CVE-2026-19867 Uncapped mention keys in user notification properties allow CPU exhaustion during post processing — Mattermost CWE-770 4.3 Medium 2026-10-16
CVE-2026-19601 Disclosure of AD/LDAP bind password via Test Connection — Mattermost CWE-201 4.9 Medium 2026-10-16
CVE-2026-18551 Mattermost guest account privilege escalation via member roles API — Mattermost CWE-863 6.5 Medium 2026-10-16
CVE-2026-19541 Outgoing OAuth connection client secret exposure during connection validation — Mattermost CWE-201 6.5 Medium 2026-10-16
CVE-2026-96260 Mattermost server missing request body size limit on plugin routes allows denial of service by an authenticated user — Mattermost CWE-789 6.5 Medium 2026-09-22
CVE-2026-96259 Mattermost server-side request forgery via OAuth endpoints configurable by a System Administrator — Mattermost CWE-918 5.5 Medium 2026-09-22
CVE-2026-95666 Unbounded post ID array in the bulk reactions endpoint allows denial of service — Mattermost CWE-770 4.3 Medium 2026-09-22
CVE-2026-12284 Mattermost Desktop App Missing IPC Sender Validation in Calls Leave Handler — Mattermost CWE-346 3.8 Low 2026-09-17
CVE-2026-75588 Mattermost Desktop App plugin popout scheme validation bypass — Mattermost CWE-1287 2.6 Low 2026-09-17
CVE-2026-75025 Mattermost Desktop local network access from server-rendered content — Mattermost CWE-346 4.7 Medium 2026-09-16
CVE-2026-91181 Data Retention Teams Endpoint Leaks Private Team Invite ID — Mattermost CWE-863 6.5 Medium 2026-09-14
CVE-2026-12985 Mattermost DCR redirect URI allowlist bypass via improper URL component validation — Mattermost CWE-601 6.8 Medium 2026-09-14
CVE-2026-82920 Mattermost ABAC parent policy bypass via policy update endpoint — Mattermost CWE-863 5.5 Medium 2026-09-14
CVE-2026-86348 MS Calendar plugin: unrecovered handler panics from malformed post-action requests could crash the plugin process — Mattermost CWE-704 4.3 Medium 2026-09-14
CVE-2026-86349 Mattermost Server Algorithmic DoS via Unbounded Markdown Block Nesting — Mattermost CWE-407 4.3 Medium 2026-09-14
CVE-2026-10556 Unauthenticated webhook request with null notification entry could crash the Microsoft Calendar plugin. — Mattermost CWE-754 5.3 Medium 2026-09-14
CVE-2026-13417 Boards plugin denial of service via unvalidated block fields.properties — Mattermost CWE-754 4.3 Medium 2026-09-14
CVE-2026-9812 Missing property field ownership validation in Playbooks run property update endpoint — Mattermost CWE-639 6.5 Medium 2026-09-14
CVE-2026-8821 Playbooks run owner channel membership permission bypass — Mattermost CWE-862 7.1 High 2026-09-14

This page lists every published CVE security advisory associated with Mattermost. Each entry links to a detailed page with CVSS scoring, CWE classification, affected products and references. AI-generated Chinese analysis is provided for fast triage.