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{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[10.11.0,10.11.12]"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[11.5.0,11.5.0]"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[11.4.0,11.4.2]"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[11.3.0,11.3.2]"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "11.6.0"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "10.11.13"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "11.5.1"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "11.4.3"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "11.3.3"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "Mattermost", "source": "cna", "vendor": "Mattermost"}, "product": "mattermost", "vendor": "mattermost"}], "analysis": {"en": {"generated_at": "2026-04-15T12:21:11.073211+00:00", "value": {"mitigation_remediation": ["Update Mattermost to version 11.6.0, 10.11.13, 11.5.1, 11.4.3, 11.3.3, or a newer release to disable token reuse.", "Revoke all outstanding guest magic link tokens before applying the patch to prevent session hijacking.", "Temporarily disable guest magic link authentication for all users until the update is applied, reducing the attack surface."], "summary": {"action": "Immediate Patch", "impact": "Unauthorized Access via Token Reuse"}, "threat_synthesis": {"affected_systems": "Mattermost; affected versions are 10.11.x up to 10.11.12, 11.5.x up to 11.5.0, 11.4.x up to 11.4.2, and 11.3.x up to 11.3.2. The advisory identifies these releases as vulnerable and recommends upgrading to 11.6.0, 10.11.13, 11.5.1, 11.4.3, or 11.3.3 and newer.", "description_and_impact": "Mattermost versions 10.11.x up to 10.11.12, 11.5.x up to 11.5.0, 11.4.x up to 11.4.2, and 11.3.x up to 11.3.2 fail to enforce atomic single\u2011use consumption of guest magic link tokens, allowing an attacker with a valid magic link to open multiple independent authenticated sessions through concurrent requests. This flaw lets an attacker impersonate any guest user, access private channels, and potentially read or modify sensitive data. The weakness is a race condition (CWE\u2011367) that compromises authentication integrity.", "risk_and_exploitability": "The CVSS score of 6.5 indicates a medium\u2011to\u2011high severity. Because the EPSS score is not available and the vulnerability is not listed in KEV, the likelihood of immediate exploitation is unknown, yet the flaw could be leveraged by anyone who has intercepted or phished a magic link. The attacker must make concurrent requests with the same magic link, a scenario that is achievable from a remote position. If successful, the attacker gains persistent, unauthenticated access until the session is terminated."}}}}, "created": "2026-04-15T13:38:17.785261+00:00", "updated": "2026-04-15T13:38:28.754573+00:00", "vendors": ["mattermost", "mattermost$PRODUCT$mattermost"]}