How severe is CVE-2026-3108?

CVE-2026-3108 has a CVSS 3.x base score of 8.0, rated high severity. It is exploitable over network with high attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-3108 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-3108?

CVE-2026-3108 primarily affects Mattermost Mattermost Server. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-3108?

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-2026-3108 have an EU (EUVD) identifier?

Yes. CVE-2026-3108 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-16234.

When was CVE-2026-3108 published?

CVE-2026-3108 was published on 2026-03-26 and last updated on 2026-06-17.

CVE-2026-3108

CVE-2026-3108 is a high-severity vulnerability in Mattermost Mattermost Server with a CVSS 3.x base score of 8.0. 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-150.

Key facts

Severity: High (CVSS 3.x base score 8.0)
EPSS exploit prediction: 0% (18th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-16234
Weakness: CWE-150
Affected product: Mattermost Mattermost Server
Published: 2026-03-26
Last modified: 2026-06-17

Description

Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to sanitize user-controlled post content in the mmctl commands terminal output which allows attackers to manipulate administrator terminals via crafted messages containing ANSI and OSC escape sequences that enable screen manipulation, fake prompts, and clipboard hijacking.. Mattermost Advisory ID: MMSA-2026-00599

Frequently asked questions

What is CVE-2026-3108?: Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to sanitize user-controlled post content in the mmctl commands terminal output which allows attackers to manipulate administrator terminals via crafted messages containing ANSI and OSC escape sequences that enable screen manipulation, fake prompts, and clipboard hijacking.. Mattermost Advisory ID: MMSA-2026-00599
How severe is CVE-2026-3108?: CVE-2026-3108 has a CVSS 3.x base score of 8.0, rated high severity. It is exploitable over network with high attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-3108 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-3108?: CVE-2026-3108 primarily affects Mattermost Mattermost Server. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-3108?: 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-2026-3108 have an EU (EUVD) identifier?: Yes. CVE-2026-3108 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-16234.
When was CVE-2026-3108 published?: CVE-2026-3108 was published on 2026-03-26 and last updated on 2026-06-17.

References

https://mattermost.com/security-updates

Affected products (2)

cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_server:11.4.0:*:*:*:*:*:*:*

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-150 vulnerabilities

CVE-2022-30123 — Critical (CVSS 10.0): A sequence injection vulnerability exists in Rack <2.0.9.1, <2.1.4.1 and <2.2.3.1 which could allow is a possible shell…
CVE-2020-6932 — Critical (CVSS 10.0): An information disclosure and remote code execution vulnerability in the slinger web server of the BlackBerry QNX…
CVE-2025-47284 — Critical (CVSS 9.9): Gardener implements the automated management and operation of Kubernetes clusters as a service. A security…
CVE-2023-26055 — Critical (CVSS 9.9): XWiki Commons are technical libraries common to several other top level XWiki projects. Starting in version…
CVE-2026-25996 — Critical (CVSS 9.8): Inspektor Gadget is a set of tools and framework for data collection and system inspection on Kubernetes clusters and…
CVE-2025-25286 — Critical (CVSS 9.8): Crayfish is a collection of Islandora 8 microservices, one of which, Homarus, provides FFmpeg as a microservice. Prior…

Browse all CWE-150 vulnerabilities →