CVE-2026-8683: Overly long URLs crash the Mattermost Desktop App

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-15 · updated 2026-06-17
Weakness: CWE-770

Description

Mattermost Desktop App versions <=6.1 5.5.13.0 fail to account for attempting to open extremely long URLs in the Mattermost Desktop App which allows a malicious server owner to crash the application via including a script to call window.open on a very large URL. Mattermost Advisory ID: MMSA-2026-00652

Affected products

Mattermost Desktop: through 5.13.0; from 6.1.0 through 6.1.5

References

https://mattermost.com/security-updates

Get alerted when CVE-2026-8683 or the next vulnerability affects your stack