{"schema_version":"1.7.5","id":"GHSA-gqv7-j2j8-qmwq","published":"2026-03-16T15:30:47Z","modified":"2026-03-23T18:56:08.125706Z","aliases":["CVE-2026-2455","GO-2026-4746"],"summary":"Mattermost fails to canonicalize IPv4-mapped IPv6 addresses before reserved IP validation","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","affected":[{"package":{"name":"github.com/mattermost/mattermost/server/v8","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost/server/v8"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"8.0.0-20260129133647-5d787969c2d5"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-gqv7-j2j8-qmwq/GHSA-gqv7-j2j8-qmwq.json"}},{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost-server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"5.3.2-0.20260129133647-5d787969c2d5"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-gqv7-j2j8-qmwq/GHSA-gqv7-j2j8-qmwq.json"}},{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost-server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"10.11.0-rc1"},{"fixed":"10.11.11"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-gqv7-j2j8-qmwq/GHSA-gqv7-j2j8-qmwq.json"}},{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost-server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"11.2.0-rc1"},{"fixed":"11.2.3"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-gqv7-j2j8-qmwq/GHSA-gqv7-j2j8-qmwq.json"}},{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost-server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"11.3.0-rc1"},{"fixed":"11.3.1"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-gqv7-j2j8-qmwq/GHSA-gqv7-j2j8-qmwq.json"}}],"references":[{"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"},{"type":"WEB","url":"https://mattermost.com/security-updates"}],"database_specific":{"cwe_ids":["CWE-918"],"github_reviewed":true,"github_reviewed_at":"2026-03-18T16:08:56Z","nvd_published_at":"2026-03-16T15:16:22Z","severity":"MODERATE"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N"}]}