CVE-2026-86349CWE-407

CVE-2026-86349

Medium · published September 14, 2026

CVSS v3.1
4.3
EPSS
0%
Percentile
29.4
In the wild
Unconfirmed
What it is

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.8, 10.11.x <= 10.11.22 fail to limit the nesting depth in the server-side Markdown parser which allows an authenticated attacker to cause a denial of service (CPU resource exhaustion) via a crafted post containing deeply nested blockquotes or list items.. Mattermost Advisory ID: MMSA-2026-00707

The record
Technical detail
CVSS v3.1
4.3 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
CVSS v4.0
Not supplied
EPSS
0.00367 · 29.4th percentile
Weakness
CWE-407 · Inefficient Algorithmic Complexity
Published
2026-09-14T18:17Z
Affected products (4)
ProductVersionsFixed in
mattermost/mattermost_server≥ 10.11.0, < 10.11.2310.11.23
mattermost/mattermost_server≥ 11.7.0, < 11.7.911.7.9
mattermost/mattermost_server≥ 11.8.0, < 11.8.511.8.5
mattermost/mattermost_server≥ 11.9.0, < 11.9.111.9.1
References (1)
https://mattermost.com/security-updates · [email protected]
EPSS history
Timeline
  • 17 SEP 03:33Z
    EPSS moved — → 0%
    epss
  • 14 SEP 13:51Z
    Mattermost Server Algorithmic DoS via Unbounded Markdown Block Nesting
    cvelistv5