CVE-2026-1046: Arbitrary application execution via unvalidated server-controlled URLs in Help menu

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: 2026-02-16 · updated 2026-10-15
Weakness: CWE-939

Description

Mattermost Desktop App versions <=6.0 6.2.0 5.2.13.0 fail to validate help links which allows a malicious Mattermost server to execute arbitrary executables on a user’s system via the user clicking on certain items in the Help menu Mattermost Advisory ID: MMSA-2026-00577

Affected products

Mattermost Desktop: from 5.13.0 before 5.13.3; from 6.0.0 before 6.0.3 — fixed in 5.13.3, 6.0.3

How to fix

Upgrade to a fixed version: Mattermost Desktop 5.13.3, 6.0.3. Check the vendor advisory for mitigations.

References

https://mattermost.com/security-updates

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