CVE•Published 2026-08-17•Modified 2026-08-19•1 article on news•6 live references•NVD data
CVE-2026-9816Mattermost · Mattermost_server
Vulnerability data via NVD (ingested)
CVSS v3.1
8.3
HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H
EPSS percentile
16
Exploit Prediction Scoring System · top 84% of all CVEs
Weaknesses (CWE)
Description
Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to validate BoardMember.Scheme* fields server-side on insert and archive-import paths which allows a board editor or non-guest team member to grant board admin to arbitrary users via POST /api/v2/boards/{boardID}/members and POST /api/v2/teams/{teamID}/archive/import.. Mattermost Advisory ID: MMSA-2026-00685
Timeline
Published 2026-08-17
Modified 2026-08-19
External references
Search for exposed instances
Shodan + Censys queries derived from NVD's CPE data. The vuln tag catches assets Shodan has explicitly linked to this CVE; the product / banner fingerprints find exposed instances even when the vuln tag was never applied (which is common).
Shodan · vuln tag0 hosts
vuln:CVE-2026-9816Hosts Shodan has explicitly fingerprinted as vulnerable.
Shodan · product
product:"Mattermost Mattermost Server"All exposed Mattermost Mattermost Server instances — cross-reference with the CVE's affected-version range.
Shodan · banner/body mention
http.html:"Mattermost Server"HTTP body or banner mentions "Mattermost Server" — catches deploys Shodan didn't identify as a product.
More intel sources (5)
Shodan report
vuln:CVE-2026-9816Country / ASN / product breakdown for the vuln query.
Censys
vulnerabilities.cve_id: CVE-2026-9816Censys host search filtered to this CVE id.
grep.app
CVE-2026-9816Public source-code mentions — fast PoC discovery.
GitHub code
CVE-2026-9816GitHub code search for direct mentions.
Google dork
"CVE-2026-9816" exploit -site:nvd.nist.govWrite-ups and news, NVD excluded.