CVE-2026-19621

EUVD-2026-102743

16.10.2026, 08:17

Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to strip action integration secrets from post payloads before broadcasting post-deletion web socket events and returning thread API responses, which allows an authenticated channel member to obtain server-side webhook URLs and authentication context from interactive-message posts via the post_deleted websocket event or the threads REST API.. Mattermost Advisory ID: MMSA-2026-00766

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
Mattermost	CNA	6.5 MEDIUM	NETWORK	LOW	LOW	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Base Score

CVSS 3.x

EPSS Score

Percentile: 15.34%

Early Detection

Affected products identified ahead of NVD analysis through intelligence sources.

Vendor	Product	Version	Source
mattermost	mattermost	𝑥 ≤ 11.10.0	CNA
mattermost	mattermost	11.7.0 ≤ 𝑥 ≤ 11.7.9	CNA
mattermost	mattermost	11.9.0 ≤ 𝑥 ≤ 11.9.1	CNA
mattermost	mattermost	11.8.0 ≤ 𝑥 ≤ 11.8.5	CNA

Common Weakness Enumeration

CWE-200 - Exposure of Sensitive Information to an Unauthorized Actor
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.

References

https://mattermost.com/security-updates