CVE-2026-19867
Uncapped mention keys in user notification properties allow CPU exhaustion during post processing
CVSS Score
4.3
EPSS Score
0.0%
EPSS Percentile
0th
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
| CWE | CWE-770 |
| Vendor | mattermost |
| Product | mattermost |
| Published | Oct 16, 2026 |
Stay Ahead of the Next One
Get instant alerts for mattermost mattermost
Be the first to know when new medium vulnerabilities affecting mattermost mattermost are published — delivered to Slack, Telegram or Discord.
Get Free Alerts →
Free · No credit card · 60 sec setup
CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low
Affected Versions
Mattermost / Mattermost
11.10.0 ≤ 11.10.0 11.9.0 ≤ 11.9.1 11.8.0 ≤ 11.8.5 11.7.0 ≤ 11.7.10
Credits
CERT PL