{"id":"CVE-2026-96259","aliases":["EUVD-2026-84869","GHSA-j85c-qqpv-57m3"],"status":"published","title":"Mattermost server-side request forgery via OAuth endpoints configurable by a System Administrator","description":"Mattermost versions 11.9.x \u003c= 11.9.1, 11.8.x \u003c= 11.8.5, 11.7.x \u003c= 11.7.10, 11.10.x \u003c= 11.10.1 fail to apply the internal-connection filter to OAuth endpoint requests, which allows a System Administrator to make the server issue requests to internal network addresses and read the responses via the configured OAuth token and userinfo endpoints.. Mattermost Advisory ID: MMSA-2026-00776","severity":{"version":"3.1","score":5.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00255,"percentile":0.17162,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-918"],"published":"2026-09-22T20:34:20Z","modified":"2026-10-28T02:30:56Z","products":[{"vendor":"mattermost","product":"mattermost"},{"vendor":"mattermost","product":"mattermost_server"}],"references":[{"url":"https://mattermost.com/security-updates","tags":["vendor-advisory","Vendor Advisory","advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-96259","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-j85c-qqpv-57m3"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/96xxx/CVE-2026-96259.json","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-96259","title":"Mattermost server-side request forgery via OAuth endpoints configurable by a System Administrator","description":"Mattermost versions 11.9.x \u003c= 11.9.1, 11.8.x \u003c= 11.8.5, 11.7.x \u003c= 11.7.10, 11.10.x \u003c= 11.10.1 fail to apply the internal-connection filter to OAuth endpoint requests, which allows a System Administrator to make the server issue requests to internal network addresses and read the responses via the configured OAuth token and userinfo endpoints.. Mattermost Advisory ID: MMSA-2026-00776","status":"published","published":"2026-09-22T20:34:20.872Z","modified":"2026-09-23T13:10:47.754Z","cvss":[{"version":"3.1","score":5.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-918"],"updated_at":"2026-11-02T14:20:00.511569Z"}],"euvd":[{"id":"EUVD-2026-84869","description":"Mattermost versions 11.9.x \u003c= 11.9.1, 11.8.x \u003c= 11.8.5, 11.7.x \u003c= 11.7.10, 11.10.x \u003c= 11.10.1 fail to apply the internal-connection filter to OAuth endpoint requests, which allows a System Administrator to make the server issue requests to internal network addresses and read the responses via the configured OAuth token and userinfo endpoints.. Mattermost Advisory ID: MMSA-2026-00776","status":"published","published":"2026-09-22T20:34:20Z","modified":"2026-09-23T13:10:47Z","cvss":[{"version":"3.1","score":5.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T17:28:01.283316Z"}],"ghsa":[{"id":"GHSA-j85c-qqpv-57m3","title":"Mattermost versions 11.9.x \u003c= 11.9.1, 11.8.x \u003c= 11.8.5, 11.7.x \u003c= 11.7.10, 11.10.x \u003c= 11.10.1...","description":"Mattermost versions 11.9.x \u003c= 11.9.1, 11.8.x \u003c= 11.8.5, 11.7.x \u003c= 11.7.10, 11.10.x \u003c= 11.10.1 fail to apply the internal-connection filter to OAuth endpoint requests, which allows a System Administrator to make the server issue requests to internal network addresses and read the responses via the configured OAuth token and userinfo endpoints.. Mattermost Advisory ID: MMSA-2026-00776","status":"published","published":"2026-09-22T21:31:31Z","modified":"2026-09-22T21:31:40Z","cvss":[{"version":"3.1","score":5.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-918"],"updated_at":"2026-11-02T15:12:19.294085Z"}],"nvd":[{"id":"CVE-2026-96259","description":"Mattermost versions 11.9.x \u003c= 11.9.1, 11.8.x \u003c= 11.8.5, 11.7.x \u003c= 11.7.10, 11.10.x \u003c= 11.10.1 fail to apply the internal-connection filter to OAuth endpoint requests, which allows a System Administrator to make the server issue requests to internal network addresses and read the responses via the configured OAuth token and userinfo endpoints.. Mattermost Advisory ID: MMSA-2026-00776","status":"published","published":"2026-09-22T21:17:34.91Z","modified":"2026-10-07T16:41:14.847Z","cvss":[{"version":"3.1","score":5.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N","level":"medium","assessor":"secondary"}],"cwes":["CWE-918"],"updated_at":"2026-11-02T14:12:50.703874Z"}],"osv":[{"id":"CVE-2026-96259","title":"Mattermost server-side request forgery via OAuth endpoints configurable by a System Administrator","description":"Mattermost versions 11.9.x \u003c= 11.9.1, 11.8.x \u003c= 11.8.5, 11.7.x \u003c= 11.7.10, 11.10.x \u003c= 11.10.1 fail to apply the internal-connection filter to OAuth endpoint requests, which allows a System Administrator to make the server issue requests to internal network addresses and read the responses via the configured OAuth token and userinfo endpoints.. Mattermost Advisory ID: MMSA-2026-00776","status":"published","published":"2026-09-22T20:34:20.872Z","modified":"2026-10-28T02:30:56.566066789Z","cvss":[{"version":"3.1","score":5.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-918"],"updated_at":"2026-11-02T15:45:21.262447Z"}]}}