Mattermost Desktop App plugin popout scheme validation bypass

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-75588
StatePUBLISHED
AssignerMattermost
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-17 16:17:41 UTC
Updated2026-09-18 13:46:33 UTC
DescriptionMattermost 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

Risk And Classification

Primary CVSS: v3.1 2.6 LOW from [email protected]

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

EPSS: 0.001670000 probability, percentile 0.063580000 (date 2026-09-20)

Problem Types: CWE-1287 | CWE-1287 CWE-1287: Improper Validation of Specified Type of Input

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary2.6LOWCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:L/A:N
3.1CNACVSS2.6LOWCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:L/A:N

CVSS v3.1 Breakdown

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

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mattermost Mattermost affected 6.2.2 semver Not specified
CNA Mattermost Mattermost unaffected 6.3.0 Not specified
CNA Mattermost Mattermost unaffected 6.2.3.0 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: Juho Forsén (en)

Additional Advisory Data

Solutions

CNA: Update Mattermost Desktop App to versions 6.3.0, 6.2.3.0 or higher.

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