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Vulnerabilities

Vulnerability · CVE-2026-27769

Mattermost 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 c…

Published Apr 15, 2026 · catalog updated Jun 17, 2026 · mattermost server

Last checked Oct 28, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-27769. EPSS is 0.17%. Act only if a listed version of mattermost server is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Low2.7
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.17%
Remediation
Version ranges on file
Affected products
cpe mattermost/mattermost server · stated mattermost server

Mattermost 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

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe mattermost/mattermost serverversion unspecified
  • stated mattermost server<= 10.11.12

How to fix CVE-2026-27769

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-27769. EPSS is 0.17%. Act only if a listed version of mattermost server is installed.

Which versions are affected?

Compare what you have installed with mattermost server <= 10.11.12. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-862: Missing Authorization. EPSS 0.17%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Apr 15, 2026 · NIST NVD

    Detected

    Mattermost 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

  2. Jun 17, 2026 · NIST NVD

    Updated

    Mattermost 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

Sources

  • CVE.orgVulnerability recordCVE-2026-27769

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-27769

    30-day exploitation probability 0.17%

    first.org
  • NIST NVDVulnerability recordCVE-2026-27769

    Mattermost 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

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 28, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSOct 28, 2026
  • CVE.orgOct 16, 2026
  • NIST NVDOct 15, 2026