Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to properly validate CSRF tokens in the /api/v4/accesscontrolpolicies/{policy_id}/activate endpoint, which allows an attacker to trick an admin into changing access control policy active status via a crafted request.. Mattermost Advisory ID: MMSA-2026-00578
{
"cna_assigner": "Mattermost",
"cwe_ids": [
"CWE-352"
],
"unresolved_ranges": [
{
"extracted_events": [
{
"introduced": "11.2.0"
},
{
"last_affected": "11.2.2"
},
{
"introduced": "10.11.0"
},
{
"last_affected": "10.11.10"
},
{
"introduced": "11.4.0"
},
{
"last_affected": "11.4.0"
},
{
"introduced": "11.3.0"
},
{
"last_affected": "11.3.1"
}
],
"source": "AFFECTED_FIELD"
}
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27659.json"
}{
"extracted_events": [
{
"introduced": "10.11.0"
},
{
"fixed": "10.11.11"
},
{
"introduced": "11.2.0"
},
{
"fixed": "11.2.3"
},
{
"introduced": "11.3.0"
},
{
"fixed": "11.3.2"
},
{
"introduced": "11.4.0"
},
{
"fixed": "11.4.1"
}
],
"cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"source": "CPE_RANGE"
}