{"cve":"CVE-2026-20796","nvd":{"published":"2026-02-13T11:16:10.280","modified":"2026-06-17T10:17:47.997","status":"Analyzed","description":"Mattermost versions 10.11.x <= 10.11.9 fail to properly validate channel membership at the time of data retrieval which allows a deactivated user to learn team names they should not have access to via a race condition in the /common_teams API endpoint.. Mattermost Advisory ID: MMSA-2025-00549","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N","score":3.1},"cwes":["CWE-367"],"references":["https://mattermost.com/security-updates"],"products":["mattermost:mattermost_server"],"source":"nvd","synced_at":"2026-10-19T22:23:35.260773158+00:00"},"epss":{"cve":"CVE-2026-20796","score":0.0022,"percentile":0.12548,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-2xf7-hmf6-p64j","url":"https://osv.dev/vulnerability/GHSA-2xf7-hmf6-p64j","summary":"Mattermost doesn't properly validate channel membership at the time of data retrieval","modified":"2026-02-23T19:41:17.607287Z","packages":[{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","purl":"pkg:golang/github.com/mattermost/mattermost-server","ranges":[">=10.11.0 <10.11.10"],"fixed":["10.11.10"]}]},{"id":"GO-2026-4495","url":"https://osv.dev/vulnerability/GO-2026-4495","summary":"Mattermost doesn't properly validate channel membership at the time of data retrieval in github.com/mattermost/mattermost-server","modified":"2026-02-23T19:41:17.607287Z","packages":[{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","purl":"pkg:golang/github.com/mattermost/mattermost-server","ranges":[">=10.11.0+incompatible <10.11.10+incompatible"],"fixed":["10.11.10+incompatible"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}