CVE-2026-19867

EUVD-2026-102808

16.10.2026, 07:17

Mattermost versions 11.10.x <= 11.10.0, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10 fail to cap the number and size of mention keys stored in a user's notification properties, and to bound the quadratic multibyte-keyword matching performed for each post, which allows an authenticated user to degrade post-processing latency and consume excessive CPU on behalf of other members of any channel they share via storing an oversized notify_props.mention_keys list on their own profile.. Mattermost Advisory ID: MMSA-2026-00773

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
Mattermost	CNA	4.3 MEDIUM	NETWORK	LOW	LOW	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

Base Score

CVSS 3.x

EPSS Score

Percentile: 10.91%

Early Detection

Affected products identified ahead of NVD analysis through intelligence sources.

Vendor	Product	Version	Source
mattermost	mattermost	𝑥 ≤ 11.10.0	CNA
mattermost	mattermost	11.9.0 ≤ 𝑥 ≤ 11.9.1	CNA
mattermost	mattermost	11.8.0 ≤ 𝑥 ≤ 11.8.5	CNA
mattermost	mattermost	11.7.0 ≤ 𝑥 ≤ 11.7.10	CNA

Common Weakness Enumeration

CWE-770 - Allocation of Resources Without Limits or Throttling
The software allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor.

References

https://mattermost.com/security-updates