[UPDATE] [medium] Mattermost: Multiple vulnerabilities allow unspecified attack

mediumCVE-2026-9571 CVE-2026-10103

An attacker can exploit multiple vulnerabilities in Mattermost to carry out an unspecified attack.

CSIRTS triage

vendor: Mattermost product: MattermostOther

What: Multiple vulnerabilities allow an attacker to carry out an unspecified attack.
Who is affected: Users of Mattermost with the affected versions.
Urgency: Remediation is medium urgency due to the unspecified nature of the attack, which could vary in impact.
Action: Check for updates from Mattermost and apply any available patches.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: CERT-Bund (BSI) Security Advisories (DE · national-cert · site)
Severity: medium
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync
Language: Machine-translated to English — verify against the original

Original advisory: https://wid.cert-bund.de/portal/wid/securityadvisory?name=WID-SEC-2026-1932

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.
Low exploitation riskCVE-2026-101030.14% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 4% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-9571	coverage & exploitation status	NVD · CVE.org
CVE-2026-10103	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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

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