How severe is CVE-2026-6346?

CVE-2026-6346 has a CVSS 3.x base score of 8.7, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2026-6346 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (21st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-6346?

CVE-2026-6346 affects Mattermost Mattermost Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-6346?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-6346 have an EU (EUVD) identifier?

Yes. CVE-2026-6346 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30754.

When was CVE-2026-6346 published?

CVE-2026-6346 was published on 2026-05-18 and last updated on 2026-06-17.

CVE-2026-6346

CVE-2026-6346 is a high-severity vulnerability in Mattermost Mattermost Server with a CVSS 3.x base score of 8.7. 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: High (CVSS 3.x base score 8.7)
EPSS exploit prediction: 0% (21st percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-30754
Weakness: CWE-200
Affected product: Mattermost Mattermost Server
Published: 2026-05-18
Last modified: 2026-06-17

Description

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to sanitize sensitive configuration fields before including them in support packet generation, which allows a Mattermost System Admin or any party with access to a support packet to obtain sensitive credentials in plaintext via downloading a support packet from the System Console.. Mattermost Advisory ID: MMSA-2026-00607

Frequently asked questions

What is CVE-2026-6346?: Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to sanitize sensitive configuration fields before including them in support packet generation, which allows a Mattermost System Admin or any party with access to a support packet to obtain sensitive credentials in plaintext via downloading a support packet from the System Console.. Mattermost Advisory ID: MMSA-2026-00607
How severe is CVE-2026-6346?: CVE-2026-6346 has a CVSS 3.x base score of 8.7, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2026-6346 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (21st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-6346?: CVE-2026-6346 affects Mattermost Mattermost Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-6346?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-6346 have an EU (EUVD) identifier?: Yes. CVE-2026-6346 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30754.
When was CVE-2026-6346 published?: CVE-2026-6346 was published on 2026-05-18 and last updated on 2026-06-17.

References

https://mattermost.com/security-updates

Affected products (1)

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

More vulnerabilities in Mattermost Mattermost Server

CVE-2025-12421 — Critical (CVSS 9.9): 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 to verify that…
CVE-2025-12419 — Critical (CVSS 9.9): Mattermost versions 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12, 11.0.x <= 11.0.3 fail to properly…
CVE-2025-4981 — Critical (CVSS 9.9): Mattermost versions 10.5.x <= 10.5.5, 9.11.x <= 9.11.15, 10.8.x <= 10.8.0, 10.7.x <= 10.7.2, 10.6.x <= 10.6.5 fail to…
CVE-2025-25279 — Critical (CVSS 9.9): Mattermost versions 10.4.x <= 10.4.1, 9.11.x <= 9.11.7, 10.3.x <= 10.3.2, 10.2.x <= 10.2.2 fail to properly validate…
CVE-2025-20051 — Critical (CVSS 9.9): Mattermost versions 10.4.x <= 10.4.1, 9.11.x <= 9.11.7, 10.3.x <= 10.3.2, 10.2.x <= 10.2.2 fail to properly validate…
CVE-2017-18920 — Critical (CVSS 9.8): An issue was discovered in Mattermost Server before 3.6.2. The WebSocket feature does not follow the Same Origin Policy.

All CVEs affecting Mattermost Mattermost Server →

Other CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) vulnerabilities

CVE-2026-27604 — Critical (CVSS 10.0): FOSSBilling is a free, open-source billing and client management system. Starting in version 0.5.4 and prior to version…
CVE-2026-40965 — Critical (CVSS 10.0): Cloud Foundry UAA versions v76.12.0 through v78.12.0 are vulnerable to a private key exposure. The server contains a…
CVE-2026-42826 — Critical (CVSS 10.0): Exposure of sensitive information to an unauthorized actor in Azure DevOps allows an unauthorized attacker to disclose…
CVE-2025-29270 — Critical (CVSS 10.0): Incorrect access control in the realtime.cgi endpoint of Deep Sea Electronics devices DSE855 v1.1.0 to v1.1.26 allows…
CVE-2025-61481 — Critical (CVSS 10.0): An issue in MikroTik RouterOS v.7.14.2 and SwOS v.2.18 exposes the WebFig management interface over cleartext HTTP by…
CVE-2025-53624 — Critical (CVSS 10.0): The Docusaurus gists plugin adds a page to your Docusaurus instance, displaying all public gists of a GitHub user.…

Browse all CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) vulnerabilities →