- 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
- Source
- responsibledisclosure@mattermost.com
- NVD status
- Analyzed
- Products
- mattermost_server
CVSS 3.1
- Type
- Secondary
- Base score
- 8.3
- Impact score
- 5.5
- Exploitability score
- 2.8
- Vector string
- CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H
- Severity
- HIGH
- responsibledisclosure@mattermost.com
- CWE-863
- Hype score
- Not currently trending
Got a bounty through Bugcrowd for two bugs I found in Mattermost: CVE-2026-9816 - CVSS 8.3/10 CVE-2026-10556 - CVSS 5.3/10 Pretty happy with this one. #BugBounty #CyberSecurity #SecurityResearch https://t.co/DOEHhVhGMO
@kamilsawickisec
14 Sept 2026
24 Impressions
0 Retweets
1 Like
0 Bookmarks
0 Replies
0 Quotes
🚨*CVE* CVE-2026-9816 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 w… https://t.co/8tysg67Ce7 ----- Traducción: CVE-2026-9816 Mat… https://t.
@infoflowcloud
17 Aug 2026
76 Impressions
0 Retweets
0 Likes
0 Bookmarks
0 Replies
0 Quotes
[
{
"nodes": [
{
"cpeMatch": [
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"criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"matchCriteriaId": "B064B1E6-B324-4701-8A07-A0B0028C73BB",
"versionEndExcluding": "10.11.22",
"versionStartIncluding": "10.11.0",
"vulnerable": true
},
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]