CVE-2026-3108

HIGH

Mattermost allows attackers to manipulate administrator terminals via crafted messages containing ANSI and OSC escape sequences

Published March 26, 2026Updated June 25, 2026Source: osv

Summary

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.

Remediation

Upgrade to the fixed version using your package manager.

Update github.com/mattermost/mattermost/server/v8 to 11.4.1 or later

go get github.com/mattermost/mattermost/server/v8@v11.4.1

Update github.com/mattermost/mattermost/server/v8 to 11.2.3 or later

go get github.com/mattermost/mattermost/server/v8@v11.2.3

Update github.com/mattermost/mattermost/server/v8 to 8.0.0-20260217110922-b7d4a1f1f59b or later

go get github.com/mattermost/mattermost/server/v8@v8.0.0-20260217110922-b7d4a1f1f59b

Update github.com/mattermost/mattermost/server/v8 to 11.3.2 or later

go get github.com/mattermost/mattermost/server/v8@v11.3.2

Update github.com/mattermost/mattermost/server/v8 to 10.11.11 or later

go get github.com/mattermost/mattermost/server/v8@v10.11.11

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (5)

Package	Ecosystem	Affected	Fixed In
github.com/mattermost/mattermost/server/v8	go	All versions	11.4.1
github.com/mattermost/mattermost/server/v8	go	All versions	11.2.3
github.com/mattermost/mattermost/server/v8	go	All versions	8.0.0-20260217110922-b7d4a1f1f59b
github.com/mattermost/mattermost/server/v8	go	All versions	11.3.2
github.com/mattermost/mattermost/server/v8	go	All versions	10.11.11

Vulnerability Classification

Common Weakness Enumeration (CWE) identifiers for this vulnerability type.

CWE-150
View on MITRE

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 8.0 score means for each attack dimension.

Attack Vector

Network

Attack Complexity

High

Privileges Required

Low

User Interaction

Required

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

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

References

https://nvd.nist.gov/vuln/detail/CVE-2026-3108
ADVISORY
https://github.com/mattermost/mattermost
PACKAGE
https://mattermost.com/security-updates
WEB

Frequently Asked Questions

What is CVE-2026-3108?: Mattermost allows attackers to manipulate administrator terminals via crafted messages containing ANSI and OSC escape sequences This vulnerability has been assigned a severity rating of HIGH (CVSS score: 8.0/10).
How do I check if my project is affected by CVE-2026-3108?: CVE-2026-3108 affects github.com/mattermost/mattermost/server/v8. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2026-3108 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score

8.0

High exploitability or significant impact. Prioritize remediation within days.

Also Known As

GHSA-3439-vqgj-2gcf

GO-2026-5067

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