What is CVE-2026-93849?

CVE-2026-93849 is a medium-severity vulnerability in Mattermost, classified under CWE-789. CVSS score: 6.5/10. Published 2026-10-26.

How severe is CVE-2026-93849?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in Mattermost

CVE-2026-93849

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

Published 2026-10-26 · last modified 2026-10-26.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Mattermost

Weakness classification (CWE)

CWE-789

References

mattermost.com/security-updates (vendor-advisory)

Frequently asked questions

What is CVE-2026-93849?: CVE-2026-93849 is a medium-severity vulnerability in Mattermost, classified under CWE-789. CVSS score: 6.5/10. Published 2026-10-26.
How severe is CVE-2026-93849?: Medium severity. CVSS v3 base score is 6.5 out of 10.