{"identifier":"CVE-2026-19621","cve":{"id":"CVE-2026-19621","description":"Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to strip action integration secrets from post payloads before broadcasting post-deletion web socket events and returning thread API responses, which allows an authenticated channel member to obtain server-side webhook URLs and authentication context from interactive-message posts via the post_deleted websocket event or the threads REST API.. Mattermost Advisory ID: MMSA-2026-00766","published":"2026-10-16T08:17:13.390000+00:00","modified":"2026-10-27T20:59:49.933000+00:00","status":"Analyzed","score":6.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","cvss_version":"3.1","affected":[{"criteria":"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*","versionStartIncluding":"11.7.0","versionStartExcluding":"","versionEndIncluding":"","versionEndExcluding":"11.7.10"},{"criteria":"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*","versionStartIncluding":"11.8.0","versionStartExcluding":"","versionEndIncluding":"","versionEndExcluding":"11.8.6"},{"criteria":"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*","versionStartIncluding":"11.9.0","versionStartExcluding":"","versionEndIncluding":"","versionEndExcluding":"11.9.2"},{"criteria":"cpe:2.3:a:mattermost:mattermost_server:11.10.0:*:*:*:*:*:*:*","versionStartIncluding":"","versionStartExcluding":"","versionEndIncluding":"","versionEndExcluding":""}],"weaknesses":["CWE-200"],"references":[{"url":"https://mattermost.com/security-updates","source":"responsibledisclosure@mattermost.com","tags":["Vendor Advisory"]}],"kev":null,"kev_checked":true,"metrics":{"cvssMetricV31":[{"source":"responsibledisclosure@mattermost.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","baseScore":6.5,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"NONE","availabilityImpact":"NONE"},"exploitabilityScore":2.8,"impactScore":3.6}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-10-16T11:58:24.369260Z","id":"CVE-2026-19621","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*","versionStartIncluding":"11.7.0","versionEndExcluding":"11.7.10","matchCriteriaId":"0D5A7979-C6DD-4EEA-B7C4-60C425EAD2C3"},{"vulnerable":true,"criteria":"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*","versionStartIncluding":"11.8.0","versionEndExcluding":"11.8.6","matchCriteriaId":"864932C7-FD92-48AC-8789-DF73D5CA9AAF"},{"vulnerable":true,"criteria":"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*","versionStartIncluding":"11.9.0","versionEndExcluding":"11.9.2","matchCriteriaId":"2F937268-2154-4B45-B9E0-8B3451070CD0"},{"vulnerable":true,"criteria":"cpe:2.3:a:mattermost:mattermost_server:11.10.0:*:*:*:*:*:*:*","matchCriteriaId":"C945CD83-FCEB-439D-8F18-02213CE7E7BF"}]}]}],"source":"nvd","retrieved_at":"2026-10-28T10:26:10.679374+00:00","exploited":false,"kev_stale":false,"products":["mattermost / mattermost server"],"priority":{"label":"Assess exposure and vendor guidance","reasons":["No higher-priority signal is available in the current stored evidence."]},"epss":{"probability":0.00255,"percentile":0.17113,"date":"2026-10-29","stale":false},"version_assessment":null},"news":[],"campaigns":[],"domains":[{"domain":"mattermost.com","source_url":"https://mattermost.com/security-updates","investigate_url":"https://investigate.aeglixmind.com/#mattermost.com"}],"arsenal_url":"https://arsenal.aeglixmind.com/?cve=CVE-2026-19621","catalog_url":"https://cves.aeglixmind.com/cve/CVE-2026-19621","research_url":"https://investigate.aeglixmind.com/research/cve/CVE-2026-19621","coverage":{"news_candidates_checked":0,"campaign_candidates_checked":0,"bounded":false,"notice":"Exact CVE mentions in stored public excerpts and reviewed campaign content only. A mention is not proof of exploitation, attribution or tool suitability. Missing matches do not establish absence."}}