CVE-2026-2299Network attack vector

Private-channel disclosure via missing membership check

Published Jun 25, 2026 · Updated Jun 25, 2026

Missing authorization in the Mattermost Google Drive Plugin before 1.1.0 allows remote authenticated users to post files to private channels. The handleFileCreation endpoint trusted a submitted channel ID and created or shared a file without calling GetChannelMember for the requester. A connected Google account and valid Mattermost session are required; exploitation reveals that a private channel exists and inserts a file post there.

CVSS severity4.2
Medium
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing authorization in the Mattermost Google Drive Plugin before 1.1.0 allows remote authenticated users to post files to private channels. The handleFileCreation endpoint trusted a submitted channel ID and created or shared a file without calling GetChannelMember for the requester. A connected Google account and valid Mattermost session are required; exploitation reveals that a private channel exists and inserts a file post there.

The record

CVE
CVE-2026-2299
Published
Jun 25, 2026
Updated
Jun 25, 2026
Vendor
Mattermost
Product
Mattermost Google Drive Plugin
Classifications
CWE-862, T1565.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 25, 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 <=1.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermost Google Drive Pluginversion=0 <=1.0.0

Published CVSS scores

4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
4.2Mattermost, Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/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.

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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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-862Missing Authorization
T1565.001Stored Data Manipulation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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