EUVD-2026-80939
GHSA-jcpq-22g2-pfpw
Severity by source
AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N
Network-delivered malicious server content requires the victim to view it (UI:R), crosses into private-network resources (S:C) for limited disclosure (C:L) with no integrity/availability impact.
Primary rating from Vendor (Mattermost).
CVSS VectorVendor: Mattermost
Lifecycle Timeline
1DescriptionCVE.org
Mattermost Desktop App versions <=6.2 6.2.2.0 Fixed an issue where Mattermost Desktop did not sufficiently restrict server-rendered content from accessing local or private network resources. Thanks to game0v3r for contributing to this improvement under the Mattermost responsible disclosure policy. Mattermost Advisory ID: MMSA-2026-00698
AnalysisAI
Insufficient origin validation in the Mattermost Desktop App (versions up to and including 6.2.2.0) lets server-rendered content from an untrusted or compromised Mattermost server reach local or private network resources, giving the attacker a limited information-disclosure window. Exploitation is not remote-only: the victim must be running the desktop client and actively connect to and view content from an attacker-controlled server (CVSS 4.7, AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N), and only confidentiality is affected - there is no integrity or availability impact. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the victim to be running the Mattermost Desktop App at version 6.2.2.0 or earlier AND to connect to and view content from an attacker-controlled or compromised Mattermost server (UI:R) - the desktop client does not sufficiently restrict that server-rendered content from reaching local or private network resources. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | This is a moderate, low-priority issue whose real-world risk is well-bounded by its own signals. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade the Mattermost Desktop App to the patched build identified in Mattermost advisory MMSA-2026-00698 (https://mattermost.com/security-updates) for all users currently on 6.2.2.0 or earlier - patch status per vendor advisory; the advisory should be consulted for the exact fixed version string rather than assuming one. … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-346 – Origin Validation Error
View allSame technique Information Disclosure
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External POC / Exploit Code
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