CVE-2026-10542

Analyzed Analyzed - Analysis Complete

Insecure Channel Action Update in Mattermost

Publication date: 2026-09-14

Last updated on: 2026-10-07

Assigner: Mattermost, Inc.

Description

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to validate channel action ownership which allows channel managers to update actions in other channels via the channel action update endpoint.. Mattermost Advisory ID: MMSA-2026-00692

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-09-14

Last Modified

2026-10-07

Generated

2026-10-19

AI Q&A

2026-09-14

EPSS Evaluated

2026-10-18

NVD

CVE-2026-10542

EUVD

EUVD-2026-77366

Affected Vendors & Products

Vendor	Product	Version / Range
mattermost	mattermost_server	From 10.11.0 (inc) to 10.11.23 (exc)
mattermost	mattermost_server	From 11.7.0 (inc) to 11.7.8 (exc)
mattermost	mattermost_server	From 11.8.0 (inc) to 11.8.5 (exc)
mattermost	mattermost_server	From 11.9.0 (inc) to 11.9.1 (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

Mattermost versions between 11.9.0 and older, 11.8.4 and older, 11.7.7 and older, and 10.11.22 and older fail to validate channel action ownership. This allows channel managers to update actions in other channels through the channel action update endpoint.

Detection Guidance

The provided CVE data does not include specific detection methods or commands for identifying this vulnerability on a network or system. Review Mattermost server logs for unauthorized channel action updates or consult their security bulletins for guidance.

Impact Analysis

An attacker with channel manager privileges could modify actions in other channels, potentially leading to unauthorized changes, data leaks, or disruption of channel functionality. This could affect team collaboration and data integrity.

Compliance Impact

This vulnerability could lead to unauthorized access or modifications, violating data integrity and confidentiality requirements in GDPR and HIPAA. Organizations using affected versions may fail compliance audits.

Mitigation Strategies

Update Mattermost to a version that fixes the vulnerability. The affected versions are 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, and 10.11.x <= 10.11.22. Check the Mattermost Security Updates page for the latest patched versions.

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