CVE-2026-9699Network attack vector

API key disclosure via unsanitized error logging

Published Jun 26, 2026 · Updated Jun 26, 2026

Sensitive-data logging in Mattermost 10.18.11, 11.3.6, and 11.6.5 and earlier allows remote authenticated users to read OpenAI API keys. The Agents plugin copies unsanitized OpenAI authentication error responses into mattermost.log, preserving complete or reconstructable credential material. Access to server logs or a support packet is required, and the resulting exposure is limited to credential disclosure.

CVSS severity6.8
Medium
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Sensitive-data logging in Mattermost 10.18.11, 11.3.6, and 11.6.5 and earlier allows remote authenticated users to read OpenAI API keys. The Agents plugin copies unsanitized OpenAI authentication error responses into mattermost.log, preserving complete or reconstructable credential material. Access to server logs or a support packet is required, and the resulting exposure is limited to credential disclosure.

The record

CVE
CVE-2026-9699
Published
Jun 26, 2026
Updated
Jun 26, 2026
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-532, T1552.001
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Jun 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 26, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=10.18.11
  2. Affected versionversion=0 <=11.3.6
  3. Affected versionversion=0 <=11.6.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Mattermost · Mattermostversion=0 <=10.18.11; version=0 <=11.3.6; version=0 <=11.6.5

Published CVSS scores

6.8Mattermost, Inc.CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-532Insertion of Sensitive Information into Log File
T1552.001Unsecured Credentials: Credentials In Files

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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