Medium severity · published Jun 26, 2026
CVE-2026-9699
Mattermost Agents plugin logs unsanitized OpenAI API keys on authentication errors
6.8
CVSS
0.5%
EPSS
No
On KEV
Description
Mattermost Plugins versions <=11.6 10.18.11 11.3.6 11.6.5.0 fail to sanitize error responses from the OpenAI API before logging, which allows a user with access to server logs or support packets to obtain a valid or partially reconstructable OpenAI API key via inspection of mattermost.log entries generated during authentication failures. Mattermost Advisory ID: MMSA-2026-00609
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
High
User interaction
None
Confidentiality
High
Integrity
None
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 40% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MA
Mattermost · Mattermost
through 10.18.11; through 11.3.6; through 11.6.5 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-9699
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-9699
mattermost.com
https://mattermost.com/security-updates
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