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CVE-2026-3108 — Vulnerability in...

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.

Advisory Timeline

  • First published March 26, 2026 (200 days ago).
  • Last revised June 25, 2026 — 91 days after initial publication.

Remediation

Upgrade to the fixed version using your package manager.

Go
Update github.com/mattermost/mattermost/server/v8 to 11.4.1 or later
go get github.com/mattermost/mattermost/server/v8@v11.4.1
Go
Update github.com/mattermost/mattermost/server/v8 to 11.2.3 or later
go get github.com/mattermost/mattermost/server/v8@v11.2.3
Go
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
Go
Update github.com/mattermost/mattermost/server/v8 to 11.3.2 or later
go get github.com/mattermost/mattermost/server/v8@v11.3.2
Go
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)

Affects 1 ecosystem: go (1).

PackageEcosystemAffectedFixed In
github.com/mattermost/mattermost/server/v8
go
All versions11.4.1
github.com/mattermost/mattermost/server/v8
go
All versions11.2.3
github.com/mattermost/mattermost/server/v8
go
All versions8.0.0-20260217110922-b7d4a1f1f59b
github.com/mattermost/mattermost/server/v8
go
All versions11.3.2
github.com/mattermost/mattermost/server/v8
go
All versions10.11.11

Vulnerability Classification

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

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

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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