CVE-2026-9571: Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to invalidate OAuth refresh tokens upon user account deactivation, which allows a deactivated user

mediumCVSS 5.9CVE-2026-9571

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to invalidate OAuth refresh tokens upon user account deactivation, which allows a deactivated user or an attacker in possession of a valid refresh token to obtain new functional access tokens via the OAuth refresh token grant endpoint.. Mattermost Advisory ID: MMSA-2026-00680

Details

Source: NVD Recent CVEs (US · database · site)
Severity: medium — CVSS 5.9
Published: 2026-07-13
Last updated: 2026-07-15
Exploitation: Not in CISA KEV at last sync

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-9571

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-95710.17% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 7% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-9571	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

medium[UPDATE] [medium] Mattermost: Multiple vulnerabilities allow unspecified attackcert-bund

Recent advisories for Mattermost

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

mediumCVE-2026-7521: Mattermost versions 11.8.x <= 11.8.0, 11.7.x <= 11.7.3, 11.6.x <= 11.6.5, 10.11.x <= 10.11.20 f…nvd · 2026-07-28
medium[UPDATE] [medium] Mattermost Server: Multiple vulnerabilitiescert-bund · 2026-07-28
mediumCVE-2026-10819: Mattermost versions 11.6.x <= 11.6.5, 10.11.x <= 10.11.20, 11.8.x <= 11.8.1, 11.7.x <= 11.7.4 …nvd · 2026-07-27
mediumCVE-2026-10600: Mattermost versions 11.8.x <= 11.8.0, 11.7.x <= 11.7.3, 11.6.x <= 11.6.5, 10.11.x <= 10.11.20 …nvd · 2026-07-27
medium[NEW] [medium] Mattermost: Multiple vulnerabilities allow unspecified attackcert-bund · 2026-07-20
unknownMultiple vulnerabilities in Mattermost Server (July 20, 2026)cert-fr-avis · 2026-07-20