Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 Fail to validate the response body of proxied images, which allows a remote attacker to enact client-side DoS via an SVG file served from an attacker-controlled origin under a non-SVG Content-Type header (e.g. image/png) embedded in an og:image meta tag or Markdown image link.. Mattermost Advisory ID: MMSA-2026-00630
{
"unresolved_ranges": [
{
"extracted_events": [
{
"introduced": "11.5.0"
},
{
"last_affected": "11.5.1"
},
{
"introduced": "10.11.0"
},
{
"last_affected": "10.11.13"
},
{
"introduced": "11.4.0"
},
{
"last_affected": "11.4.3"
}
],
"source": "AFFECTED_FIELD"
}
],
"cna_assigner": "Mattermost",
"cwe_ids": [
"CWE-754"
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/4xxx/CVE-2026-4054.json"
}{
"extracted_events": [
{
"introduced": "10.11.0"
},
{
"fixed": "10.11.14"
},
{
"introduced": "11.4.0"
},
{
"fixed": "11.4.4"
},
{
"introduced": "11.5.0"
},
{
"fixed": "11.5.2"
}
],
"cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"source": "CPE_RANGE"
}