EUVD-2026-30757
Improper Authorization in Handler for Custom URL Scheme (CWE-939)
GHSA-fhqj-97rr-gvhp
6.5
CVSS 3.1
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CVSS VectorNVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Lifecycle Timeline
1
Analysis Generated
May 18, 2026 - 09:32 vuln.today
DescriptionNVD
Mattermost Desktop App versions <=6.1 6.0.1 5.4.13.0 fail to prevent an invalid URL from loading in a pop-up window in the Mattermost Desktop App which allows a malicious server owner to repeated crash the application via calling {{window.open('javascript:alert()');}}. Mattermost Advisory ID: MMSA-2026-00618
AnalysisAI
Mattermost Desktop App can be repeatedly crashed by malicious server administrators through JavaScript URL injection in pop-up windows. Attackers controlling a Mattermost server can force connected desktop clients to become unusable by exploiting improper URL validation, requiring user interaction (connecting to the malicious server). …
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External POC / Exploit Code
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