Connected Workspaces: Malicious remote server can manipulate arbitrary user's status

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Summary

CVECVE-2026-27769
StatePUBLISHED
AssignerMattermost
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-15 11:16:33 UTC
Updated2026-04-22 19:43:52 UTC
DescriptionMattermost versions 10.11.x <= 10.11.12 fail to validate whether users were correctly owned by the correct Connected Workspace which allows a malicious remote server connected using the Conntexted Workspaces feature to change the displayed status of local users via the Connected Workspaces API.. Mattermost Advisory ID: MMSA-2026-00603

Risk And Classification

Primary CVSS: v3.1 2.7 LOW from [email protected]

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

EPSS: 0.000320000 probability, percentile 0.092530000 (date 2026-04-22)

Problem Types: CWE-862 | CWE-862 CWE-862: Missing Authorization

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary2.7LOWCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:N
3.1CNACVSS2.7LOWCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:N

CVSS v3.1 Breakdown

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

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Mattermost Mattermost Server All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mattermost Mattermost affected 10.11.0 10.11.12 semver Not specified
CNA Mattermost Mattermost unaffected 11.5.0 Not specified
CNA Mattermost Mattermost unaffected 10.11.13 Not specified

References

ReferenceSourceLinkTags
mattermost.com/security-updates [email protected] mattermost.com Vendor Advisory
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: daw10 (en)

Additional Advisory Data

Solutions

CNA: Update Mattermost to versions 11.5.0, 10.11.13 or higher.

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