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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.

CVE ID Title CVSS Severity Published
CVE-2026-4053 post edit time limit is not enforced on some post update operations — Mattermost CWE-672 3.1 Low 2026-05-15
CVE-2026-4054 SVG content served through Mattermost image proxy despite Content-Type restrictions causes client-side denial of service — Mattermost CWE-754 4.3 Medium 2026-05-15
CVE-2026-3590 Race Condition in Guest Magic Link Authentication Allows Token Reuse — Mattermost CWE-367 6.5 Medium 2026-04-15
CVE-2026-28741 CSRF Protection Bypass Allows Updating a User's Authentication Method — Mattermost CWE-352 6.8 Medium 2026-04-15
CVE-2026-27769 Connected Workspaces: Malicious remote server can manipulate arbitrary user's status — Mattermost CWE-862 2.7 Low 2026-04-15
CVE-2026-24661 Unbounded Request Body Read in MS Teams Plugin {{/changes}} Webhook Endpoint — Mattermost CWE-770 3.7 Low 2026-04-09
CVE-2026-21388 Unbounded Request Body Read in MS Teams Plugin {{/lifecycle}} Webhook Endpoint — Mattermost CWE-770 3.7 Low 2026-04-09
CVE-2026-3524 Authorization Bypass in Mattermost Legal Hold Plugin Due to Missing Return After Permission Check — Mattermost CWE-862 8.3 High 2026-04-06
CVE-2026-28736 Focalboard IDOR in file content endpoint allows cross-user file access (unsupported product, no fix) — Focalboard CWE-639 4.3 Medium 2026-04-03
CVE-2026-25773 Focalboard Second-Order SQL Injection in category reorder endpoint allows data exfiltration (unsupported product, no fix) — Focalboard CWE-89 8.1 High 2026-04-03
CVE-2026-3112 Arbitrary File Read via Advanced Logging Support Packet — Mattermost CWE-22 6.8 Medium 2026-03-26
CVE-2026-3109 Missing timestamp validation in Zoom webhook handler — Mattermost CWE-754 2.2 Low 2026-03-26
CVE-2026-3115 Guest users can view group member IDs without respecting view restrictions — Mattermost CWE-863 4.3 Medium 2026-03-26
CVE-2026-3114 Zip Bomb Denial of Service via Unrestricted Archive Decompression — Mattermost CWE-409 6.5 Medium 2026-03-26
CVE-2026-3116 Improper Input Validation in Zoom Plugin Webhook Handler — Mattermost CWE-400 4.9 Medium 2026-03-26
CVE-2026-3113 mmctl export download command doesn’t restrict permissions to created file to file owner — Mattermost CWE-732 5.0 Medium 2026-03-26
CVE-2026-3108 Terminal Escape Injection in mmctl Report Posts Command — Mattermost CWE-150 8.0 High 2026-03-26
CVE-2026-4274 Insufficient authorization in shared channel membership sync grants team-level access instead of channel-level access — Mattermost CWE-863 5.4 Medium 2026-03-26
CVE-2026-27659 CSRF vulnerability in UpdateAccessControlPolicyActiveStatus endpoint — Mattermost CWE-352 4.6 Medium 2026-03-25
CVE-2026-20719 DoS via URL Previews Rendering Malicious SVGs — Mattermost CWE-754 4.3 Medium 2026-03-25
CVE-2026-27656 Account Takeover via Substring Matching in OpenID Connect Authentication — Mattermost CWE-303 5.7 Medium 2026-03-25
CVE-2026-26233 Denial of Service via HTTP/2 single packet attack on login endpoint — Mattermost CWE-400 4.3 Medium 2026-03-25
CVE-2026-1629 Permalink Preview Information Disclosure After Permission Revocation — Mattermost CWE-672 4.3 Medium 2026-03-16
CVE-2026-26230 Team Admin Privilege Escalation to Demote Members to Guest — Mattermost CWE-863 3.8 Low 2026-03-16
CVE-2026-2454 DoS in Calls plugin via malformed msgpack in websocket request. — Mattermost CWE-1287 5.8 Medium 2026-03-16
CVE-2026-26304 Permission Bypass in Playbook Run Creation — Mattermost CWE-863 4.3 Medium 2026-03-16
CVE-2026-24692 Guest users can bypass read permissions via search API — Mattermost CWE-863 4.3 Medium 2026-03-16
CVE-2026-22545 Password Change Bypass via Auth Switch Endpoint — Mattermost CWE-863 3.1 Low 2026-03-16
CVE-2026-2455 SSRF bypass via IPv4-mapped IPv6 literals — Mattermost CWE-918 4.3 Medium 2026-03-16
CVE-2026-21386 Private channel enumeration via /mute slash command — Mattermost CWE-203 4.3 Medium 2026-03-16

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.