Opening a window with {{javascript:alert()}} as URL causes crash in the Mattermost Desktop App

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Summary

CVECVE-2026-3471
StatePUBLISHED
AssignerMattermost
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-18 09:16:22 UTC
Updated2026-05-18 17:32:38 UTC
DescriptionMattermost 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

Risk And Classification

Primary CVSS: v3.1 6.5 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

EPSS: 0.000380000 probability, percentile 0.114050000 (date 2026-05-26)

Problem Types: CWE-939 | CWE-939 CWE-939: Improper Authorization in Handler for Custom URL Scheme

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
3.1CNACVSS6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mattermost Mattermost affected 6.0.1 semver Not specified
CNA Mattermost Mattermost affected 5.4.13 semver Not specified
CNA Mattermost Mattermost unaffected 6.2.0 Not specified
CNA Mattermost Mattermost unaffected 6.1.1.0 Not specified
CNA Mattermost Mattermost unaffected 5.13.5.0 Not specified

References

ReferenceSourceLinkTags
mattermost.com/security-updates [email protected] mattermost.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: game0v3r (en)

Additional Advisory Data

Solutions

CNA: Update Mattermost Desktop App to versions 6.2.0, 6.1.1.0, 5.13.5.0 or higher.

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