Mattermost allows authenticated users to trigger excessive memory allocation via crafted msgpack binary WebSocket frames
Summary
| CVE | CVE-2026-93849 |
|---|---|
| State | PUBLISHED |
| Assigner | Mattermost |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-10-26 15:16:46 UTC |
| Updated | 2026-10-26 17:17:31 UTC |
| Description | Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 Mattermost fail to apply allocation limits to the byte-string decode paths in its WebSocket msgpack decoder, which allows an authenticated remote attacker to cause excessive server memory allocation via a crafted binary WebSocket frame declaring a Bin32 payload length of up to 4,294,967,295 bytes.. Mattermost Advisory ID: MMSA-2026-00768 |
Risk And Classification
Primary CVSS: v3.1 6.5 MEDIUM from [email protected]
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Problem Types: CWE-789 | CWE-789 CWE-789: Memory Allocation with Excessive Size Value
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 6.5 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | CNA | CVSS | 6.5 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
LowUser Interaction
NoneScope
UnchangedConfidentiality
NoneIntegrity
NoneAvailability
HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Mattermost | Mattermost | affected 11.9.0 11.9.1 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 11.8.0 11.8.5 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 11.7.0 11.7.10 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 11.10.0 11.10.1 semver | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.11.0 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.9.2 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.8.6 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.7.11 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.10.2 | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| mattermost.com/security-updates | [email protected] | mattermost.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: oduoke (en)
Additional Advisory Data
Solutions
CNA: Update Mattermost to versions 11.11.0, 11.9.2, 11.8.6, 11.7.11, 11.10.2 or higher.
There are currently no legacy QID mappings associated with this CVE.