Medium severity · published Mar 2, 2026
CVE-2026-1628
Mattermost allows external websites to open within the app, exposing preload functionality to non-trusted sites.
4.6
CVSS
0.1%
EPSS
No
On KEV
Description
Mattermost Desktop App versions <=5.13.3 fail to attach listeners restricting navigation to external sites within the Mattermost app which allows a malicious server to expose preload script functionality to untrusted servers via having a user open an external link in their Mattermost server. Mattermost Advisory ID: MMSA-2026-00596
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.1% · higher than 4% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MA
Mattermost · Mattermost
through 5.13.3 · source: vendor
MD
Mattermost Desktop · Mattermost
before 5.13.4 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-1628
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-1628
Vendor Advisory
https://mattermost.com/security-updates
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