Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.2, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate the TIFF IFD offset in the image header before allocating memory, which allows authenticated users with file upload or posting permissions to cause a denial of service (server OOM) via uploading a crafted TIFF file or posting a URL that serves one.. Mattermost Advisory ID: MMSA-2026-00648
{
"unresolved_ranges": [
{
"source": "AFFECTED_FIELD",
"extracted_events": [
{
"introduced": "11.6.0"
},
{
"last_affected": "11.6.0"
},
{
"introduced": "11.5.0"
},
{
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},
{
"introduced": "11.5.0"
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{
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{
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{
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},
{
"introduced": "10.11.0"
},
{
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}
]
}
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5755.json",
"cna_assigner": "Mattermost",
"cwe_ids": [
"CWE-400"
]
}{
"source": "CPE_RANGE",
"cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"extracted_events": [
{
"introduced": "10.11.0"
},
{
"fixed": "10.11.15"
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{
"introduced": "11.4.0"
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{
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{
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{
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{
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{
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}
]
}