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CVE-2026-9699

Mattermost Agents plugin logs unsanitized OpenAI API keys on authentication errors

MEDIUM
6.8
CVSS Score
Published: June 26, 2026 at 02:43 PM UTC
Updated: June 27, 2026 at 11:42 AM UTC
1 product affected across 1 vendorMattermost

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Severity
MEDIUM6.8
Exploit prediction
EPSS 0.5%
SSVC
No known exploit

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

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Mattermost· Mattermost
60%
v ≤ 10.18.11v ≤ 11.3.6v ≤ 11.6.5
Vendor states this is fixed in 10.11.19 (unaffected)
Vendor states this is fixed in 11.5.7 (unaffected)
Vendor states this is fixed in 11.6.4 (unaffected)
Vendor states this is fixed in 11.7.0 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (1)

Vendor Advisory
Source: cverecord
https://mattermost.com/security-updates

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.8MEDIUMMattermost
Attack Vector
NETWORK
Complexity
LOW
Privileges
HIGH
User Interaction
NONE
Scope
CHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusAWAITING ANALYSIS
CWE
CWE-532

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