{"id":"CVE-2026-2456","aliases":["GHSA-34g8-9fpp-46ch","GO-2026-4726"],"url":"https://o3.security/vulnerability/CVE-2026-2456","summary":"Denial of Service via Unbounded Memory Allocation in Integration Actions","details":"Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 Mattermost fails to limit the size of responses from integration action endpoints, which allows an authenticated attacker to cause server memory exhaustion and denial of service via a malicious integration server that returns an arbitrarily large response when a user clicks an interactive message button.. Mattermost Advisory ID: MMSA-2026-00571","published":"2026-03-16T11:06:44.920Z","modified":"2026-09-18T03:46:19.951412190Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H"},"epss":{"score":0.00165,"percentile":0.06109,"asOf":"2026-08-08"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/mattermost/mattermost/server/v8","fixedVersion":"8.0.0-20260127165411-fe3052073dc6"},{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","fixedVersion":"5.3.2-0.20260127165411-fe3052073dc6"},{"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/fe3052073dc67e3c920baf9fe7efd44ac1d8124c","label":"mattermost/mattermost@fe30520"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/2xxx/CVE-2026-2456.json"},{"type":"ADVISORY","url":"https://mattermost.com/security-updates"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-2456"},{"type":"WEB","url":"https://github.com/mattermost/mattermost/commit/fe3052073dc67e3c920baf9fe7efd44ac1d8124c"},{"type":"PACKAGE","url":"https://github.com/mattermost/mattermost"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-18T03:46:19.951412190Z"}}