CVE-2026-6062

Analyzed Analyzed - Analysis Complete

Subscription Hijacking in Mattermost

Publication date: 2026-06-22

Last updated on: 2026-06-23

Assigner: Mattermost, Inc.

Description

Mattermost versions 11.7.x <= 11.7.0, 11.6.x <= 11.6.2, 11.5.x <= 11.5.5, 10.11.x <= 10.11.17 Fail to validate channel ownership of an existing subscription before applying edits which allows an authenticated attacker to hijack subscriptions from channels they have no access to via a crafted PUT request to the subscription edit endpoint.. Mattermost Advisory ID: MMSA-2026-00650

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-06-22

Last Modified

2026-06-23

Generated

2026-07-13

AI Q&A

2026-06-22

EPSS Evaluated

2026-07-11

NVD

CVE-2026-6062

EUVD

EUVD-2026-38250

Affected Vendors & Products

Vendor	Product	Version / Range
mattermost	mattermost_server	From 10.11.0 (inc) to 10.11.18 (exc)
mattermost	mattermost_server	From 11.7.0 (inc) to 11.7.1 (exc)
mattermost	mattermost_server	From 11.5.0 (inc) to 11.5.6 (exc)
mattermost	mattermost_server	From 11.6.0 (inc) to 11.6.3 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-639	The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.

Attack-Flow Graph

Executive Summary

This vulnerability exists in certain versions of Mattermost where the system fails to validate channel ownership before allowing edits to existing subscriptions. Specifically, an authenticated attacker can hijack subscriptions from channels they do not have access to by sending a crafted PUT request to the subscription edit endpoint.

Impact Analysis

The vulnerability allows an attacker with authentication to hijack subscriptions from channels they should not have access to. This can lead to unauthorized access to information or notifications from those channels, potentially compromising confidentiality and integrity of data within the Mattermost environment.

Compliance Impact

The provided information does not specify how this vulnerability impacts compliance with common standards and regulations such as GDPR or HIPAA.

Mitigation Strategies

To mitigate this vulnerability, you should update Mattermost to a version later than the affected versions (above 11.7.0, 11.6.2, 11.5.5, and 10.11.17) where the issue has been fixed.

Additionally, monitor Mattermost security updates and advisories regularly to apply patches promptly.

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