CVE-2024-39777: mattermost Access Control Flaw — Fix

Description

Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to disallow unsolicited invites to expose access to local channels, when shared channels are enabled, which allows a malicious remote to send an invite with the ID of an existing local channel, and that local channel will then become shared without the consent of the local admin.

Is your site exposed to CVE-2024-39777?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

8.7

HIGH

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

Weakness Type (CWE)

CWE-284 CWE-284

Affected Products

Vendor	Product	Versions
mattermost	mattermost	9.5.0 — 9.5.7
mattermost	mattermost	9.7.0 — 9.7.6
mattermost	mattermost	9.8.0 — 9.8.2
mattermost	mattermost	All

References

Advisories & Patches

https://mattermost.com/security-updates

Frequently Asked Questions

What is CVE-2024-39777? +

Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to disallow unsolicited invites to expose access to local channels, when shared channels are enabled, which allows a malicious remote to send an invite with the ID of an existing local channel, and that local channel will then become shared without the consent of the local admin. It has a CVSS v3.1 base score of 8.7 (HIGH).

How severe is CVE-2024-39777? +

CVE-2024-39777 has a CVSS v3.1 score of 8.7 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2024-39777? +

CVE-2024-39777 affects products from mattermost, specifically: mattermost. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2024-39777? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-35402

mcp-neo4j-cypher is an MCP server for executing Cypher queries against Neo4j databases. In versions prior to 0.6.0, the read_only mode …

CVE-2026-40866

Horilla is a free and open source Human Resource Management System (HRMS). In 1.5.0, an insecure direct object reference in …

CVE-2026-40865

Horilla is a free and open source Human Resource Management System (HRMS). In 1.5.0, an insecure direct object reference in …

CVE-2026-40874

mailcow: dockerized is an open source groupware/email suite based on docker. In versions prior to 2026-03b, no administrator verification takes …

CVE-2026-54533

vantage6 is an open-source infrastructure for privacy preserving analysis. Prior to version 5.0.0, malicious algorithms can potentially access other algorithms …

CVE-2026-48907

A vulnerability in the JCE editor extension for Joomla allows the creation of new editor profiles for unauthenticated users, ultimately …

CVE-2024-39777