CVE-2026-9708

What it is

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to validate that an assigned incoming webhook user has access to the target team or channel, which allows a requester with webhook management permissions to create posts or direct messages attributed to another user via crafted incoming webhook configuration and payloads.. Mattermost Advisory ID: MMSA-2026-00683

At a glance

Exploitability

Can be exploited over the network with an admin-level account. High risk of data tampering.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-07-13 09:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-07-13 20:39 UTC Last updatedMost recent change to the record

Details

Published

2026-07-13 09:16 UTC

Last modified

2026-07-13 20:39 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-639 · Insecure direct object reference

Record status

Analyzed

Affected

• Mattermost Server < 10.11.20
• Mattermost Server < 11.6.5
• Mattermost Server < 11.7.3

Attack profile CVSS 3.1 · 4.9

Attack vector

Network

Complexity

Low

Privileges needed

High

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

High

Availability

None