High severity · published Mar 16, 2026
CVE-2026-2454
DoS in Calls plugin via malformed msgpack in websocket request.
8.6
CVSS
0.3%
EPSS
No
On KEV
Description
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to handle incorrectly reported array lengths which allows malicious user to cause OOM errors and crash the server via sending corrupted msgpack frames within websocket messages to calls plugin. Mattermost Advisory ID: MMSA-2025-00537
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 21% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MA
Mattermost · Mattermost
11.3.0 through 11.3.0; 11.2.0 through 11.2.2; 10.11.0 through 10.11.10 · source: vendor
MS
Mattermost Server · Mattermost
10.11.0 before 10.11.11; 11.2.0 before 11.2.3; 11.3.0 before 11.3.1 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-2454
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-2454
Vendor Advisory
https://mattermost.com/security-updates
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