{"id":"CVE-2026-2455","aliases":["GHSA-gqv7-j2j8-qmwq","GO-2026-4746"],"url":"https://o3.security/vulnerability/CVE-2026-2455","summary":"SSRF bypass via IPv4-mapped IPv6 literals","details":"Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to canonicalize IPv4-mapped IPv6 addresses before reserved IP validation which allows an attacker to perform SSRF attacks against internal services via IPv4-mapped IPv6 literals (e.g., [::ffff:127.0.0.1]).. Mattermost Advisory ID: MMSA-2026-00585","published":"2026-03-16T14:53:31.280Z","modified":"2026-09-18T03:46:19.602121036Z","cvss":{"score":4.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Go","name":"github.com/mattermost/mattermost/server/v8","fixedVersion":"8.0.0-20260129133647-5d787969c2d5"},{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","fixedVersion":"5.3.2-0.20260129133647-5d787969c2d5"},{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","fixedVersion":"10.11.11"},{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","fixedVersion":"11.2.3"},{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","fixedVersion":"11.3.1"}],"fix":{"url":"https://github.com/mattermost/mattermost/commit/5d787969c2d5ab591a9dcd61b0810475eed7a646","label":"mattermost/mattermost@5d78796"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/2xxx/CVE-2026-2455.json"},{"type":"ADVISORY","url":"https://mattermost.com/security-updates"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-2455"},{"type":"WEB","url":"https://github.com/mattermost/mattermost/commit/5d787969c2d5ab591a9dcd61b0810475eed7a646"},{"type":"PACKAGE","url":"https://github.com/mattermost/mattermost"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-18T03:46:19.602121036Z"}}