{"id":"GHSA-5gmf-x7hg-97wf","summary":"Mattermost doesn't filter nil elements from outgoing webhook attachment payloads before processing","details":"Mattermost versions 11.6.x \u003c= 11.6.0, 11.5.x \u003c= 11.5.3, 11.4.x \u003c= 11.4.4, 10.11.x \u003c= 10.11.14 fail to filter nil elements from outgoing webhook attachment payloads before processing, which allows an authenticated user to cause a denial of service (server process termination) via a crafted webhook callback response containing a null attachment entry. Mattermost Advisory ID: MMSA-2026-00641","aliases":["CVE-2026-4915","GO-2026-5845"],"modified":"2026-07-07T16:11:44.059616444Z","published":"2026-05-26T13:30:40Z","database_specific":{"cwe_ids":["CWE-754"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-06-30T16:58:39Z","nvd_published_at":"2026-05-25T08:16:24Z"},"references":[{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-4915"},{"type":"WEB","url":"https://github.com/mattermost/mattermost/commit/faa7d75b4ea041701e97948f8aa1332e3626a39a"},{"type":"PACKAGE","url":"https://github.com/mattermost/mattermost"},{"type":"WEB","url":"https://mattermost.com/security-updates"}],"affected":[{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost-server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"11.6.0"},{"fixed":"11.6.1"}]}],"versions":["11.6.0"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-5gmf-x7hg-97wf/GHSA-5gmf-x7hg-97wf.json"}},{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost-server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"11.5.0"},{"fixed":"11.5.4"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-5gmf-x7hg-97wf/GHSA-5gmf-x7hg-97wf.json"}},{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost-server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"11.4.0"},{"fixed":"11.4.5"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-5gmf-x7hg-97wf/GHSA-5gmf-x7hg-97wf.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"},{"fixed":"10.11.15"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-5gmf-x7hg-97wf/GHSA-5gmf-x7hg-97wf.json"}},{"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":"8.0.0-20260407102538-faa7d75b4ea0"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-5gmf-x7hg-97wf/GHSA-5gmf-x7hg-97wf.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}