{"id":"CVE-2026-95666","summary":"Unbounded post ID array in the bulk reactions endpoint allows denial of service","details":"Mattermost versions 11.9.x \u003c= 11.9.1, 11.8.x \u003c= 11.8.5, 11.7.x \u003c= 11.7.10, 11.10.x \u003c= 11.10.1 fail to limit the length of the post ID array accepted by the bulk reactions endpoint which allows an authenticated user to cause excessive database load via a crafted request to {{POST /api/v4/posts/ids/reactions}}.. Mattermost Advisory ID: MMSA-2026-00771","modified":"2026-10-09T02:49:30.878403143Z","published":"2026-09-22T13:11:13.798Z","database_specific":{"cna_assigner":"Mattermost","cwe_ids":["CWE-770"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/95xxx/CVE-2026-95666.json","unresolved_ranges":[{"extracted_events":[{"introduced":"11.9.0"},{"last_affected":"11.9.1"},{"introduced":"11.8.0"},{"last_affected":"11.8.5"},{"introduced":"11.7.0"},{"last_affected":"11.7.10"},{"introduced":"11.10.0"},{"last_affected":"11.10.1"}],"source":"AFFECTED_FIELD"}]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/95xxx/CVE-2026-95666.json"},{"type":"ADVISORY","url":"https://mattermost.com/security-updates"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-95666"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/mattermost/mattermost","events":[{"introduced":"a9e574a82633915f22071f0d7ca2b006f249ec2a"},{"fixed":"062eb3ba0e0f265bd0bc78d8c5ce5df06b7b6bc8"},{"introduced":"583461af10fc9b2aef2871c722fc4376db695832"},{"fixed":"8ed7691c22159afec427468b8a866aeeaf59a12c"},{"introduced":"7f5bffb8cf3977db8237ce10158fa22aa0d2504f"},{"fixed":"3a01fa64e5c292bd2503de37160cae10e10096de"}],"database_specific":{"source":"CPE_RANGE","cpe":"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"11.7.0"},{"fixed":"11.7.11"},{"introduced":"11.9.0"},{"fixed":"11.9.2"},{"introduced":"11.10.0"},{"fixed":"11.10.2"}]}}],"versions":["v11.7.10","v11.10.1","v11.7.9","v11.9.1-rc1","v11.9.1","v11.10.0-rc3","v11.10.0","v11.7.8","v11.7.7","v11.9.0","mattermost-redux@11.9.0","@mattermost/types@11.9.0","@mattermost/shared@11.9.0","@mattermost/client@11.9.0","v11.7.6","v11.7.5-rc1","v11.7.5","v11.7.4","v11.7.3","v11.7.2","v11.7.1","v11.7.0","mattermost-redux@11.7.0","@mattermost/types@11.7.0","@mattermost/shared@11.7.0","@mattermost/client@11.7.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-95666.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:L"}]}