CVE-2026-9708 json
Incoming webhook user attribution via unvalidated webhook owner
published 2026-07-13 3 mo ago modified 2026-07-13 3 mo ago also EUVD-2026-43308
- cvss
- 4.9
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 30%
- public exploits
- 0
- none known
Summary
Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to validate that an assigned incoming webhook user has access to the target team or channel, which allows a requester with webhook management permissions to create posts or direct messages attributed to another user via crafted incoming webhook configuration and payloads.. Mattermost Advisory ID: MMSA-2026-00683
Patch / fix
- Mattermost Mattermost 10.11.20, 11.6.5, 11.7.3, 11.8.0
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 3 mo ago
Exploit prediction
0.36% chance of exploitation in the next 30 days, higher than 30% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 4.9 | CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N |
Affected products
- Mattermost Mattermost
Classification
- Weakness
-
- CWE-639 Authorization Bypass Through User-Controlled Key
References
-
mattermost.com
/security-updates
vendor-advisory
Sources
- CVE List CVE-2026-9708
- NVD CVE-2026-9708
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.