How severe is CVE-2025-12559?

CVE-2025-12559 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2025-12559 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (9th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-12559?

CVE-2025-12559 affects Mattermost Mattermost Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-12559?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-12559 have an EU (EUVD) identifier?

Yes. CVE-2025-12559 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-199831.

When was CVE-2025-12559 published?

CVE-2025-12559 was published on 2025-11-27 and last updated on 2026-06-17.

CVE-2025-12559

CVE-2025-12559 is a medium-severity vulnerability in Mattermost Mattermost Server with a CVSS 3.x base score of 4.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-200.

Key facts

Severity: Medium (CVSS 3.x base score 4.3)
EPSS exploit prediction: 0% (9th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-199831
Weakness: CWE-200
Affected product: Mattermost Mattermost Server
Published: 2025-11-27
Last modified: 2026-06-17

Description

Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to sanitize team email addresses to be visible only to Team Admins, which allows any authenticated user to view team email addresses via the GET /api/v4/channels/{channel_id}/common_teams endpoint

Frequently asked questions

What is CVE-2025-12559?: Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to sanitize team email addresses to be visible only to Team Admins, which allows any authenticated user to view team email addresses via the GET /api/v4/channels/{channel_id}/common_teams endpoint
How severe is CVE-2025-12559?: CVE-2025-12559 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2025-12559 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (9th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-12559?: CVE-2025-12559 affects Mattermost Mattermost Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-12559?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-12559 have an EU (EUVD) identifier?: Yes. CVE-2025-12559 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-199831.
When was CVE-2025-12559 published?: CVE-2025-12559 was published on 2025-11-27 and last updated on 2026-06-17.

References

https://mattermost.com/security-updates

Affected products (1)

cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*

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