CVE-2026-75588

LOW 2.6

Mattermost Desktop App plugin popout scheme validation bypass

CVSS Score

2.6

EPSS Score

0.0%

EPSS Percentile

0th

Mattermost Desktop App versions <=6.2 6.2.2.0 fail to validate the URL scheme when checking whether a target URL is internal to the connected server, which allows a network-positioned attacker to load a plugin popout window over an insecure connection via a link using a downgraded URL scheme. Mattermost Advisory ID: MMSA-2026-00717

CWE	CWE-1287
Vendor	mattermost
Product	mattermost
Published	Sep 17, 2026

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CVSS v3 Breakdown

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

Attack Vector

Network

Attack Complexity

High

Privileges Required

Low

User Interaction

Required

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

None

Affected Versions

Mattermost / Mattermost

0 ≤ 6.2.2

References

NVD ↗ CVE.org ↗ EPSS Data ↗

mattermost.com: https://mattermost.com/security-updates

Credits

Juho Forsén