Medium severity · published May 18, 2026
CVE-2026-3471
Opening a window with {{javascript:alert()}} as URL causes crash in the Mattermost Desktop App
6.5
CVSS
0.2%
EPSS
No
On KEV
Description
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
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 8% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MA
Mattermost · Mattermost
through 6.0.1; through 5.4.13 · source: vendor
MD
Mattermost Desktop · Mattermost
through 5.4.13.0; 6.0.0 through 6.0.1; 6.1.0 before 6.2.0 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-3471
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-3471
Vendor Advisory
https://mattermost.com/security-updates
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