CVE-2025-14822: DoS from quadratic complexity in model.ParseHashtags

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-01-16 · updated 2026-06-17
Weakness: CWE-407

Description

Mattermost versions 10.11.x <= 10.11.8 fail to validate input size before processing hashtags which allows an authenticated attacker to exhaust CPU resources via a single HTTP request containing a post with thousands space-separated tokens

Affected products

Mattermost: from 10.11.0 before 10.11.9 — fixed in 10.11.9

How to fix

Upgrade to a fixed version: Mattermost 10.11.9. Check the vendor advisory for mitigations.

References

https://mattermost.com/security-updates

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