CVE-2026-28732Network attack vector

Command hijacking via unchecked slash-command trigger updates

Published May 18, 2026 · Updated May 18, 2026

Incorrect authorization in Mattermost 10.11.0 through 10.11.13, 11.4.0 through 11.4.3, and 11.5.0 through 11.5.1 allows command hijacking. UpdateCommand saved an edited trigger without checking it case-insensitively against built-in commands or other commands registered to the team. Remote authenticated users with Manage Own Slash Commands permission can reuse a trusted trigger, causing later invocations to be routed to the malicious command URL.

CVSS severity4.3
Medium
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect authorization in Mattermost 10.11.0 through 10.11.13, 11.4.0 through 11.4.3, and 11.5.0 through 11.5.1 allows command hijacking. UpdateCommand saved an edited trigger without checking it case-insensitively against built-in commands or other commands registered to the team. Remote authenticated users with Manage Own Slash Commands permission can reuse a trusted trigger, causing later invocations to be routed to the malicious command URL.

The record

CVE
CVE-2026-28732
Published
May 18, 2026
Updated
May 18, 2026
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-863, T1036
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 18, 2026CVE publishedPublication date reported by the CVE source.
  2. May 18, 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=10.11.0 <=10.11.13
  2. Affected versionversion=11.4.0 <=11.4.3
  3. Affected versionversion=11.5.0 <=11.5.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermostversion=10.11.0 <=10.11.13; version=11.4.0 <=11.4.3; version=11.5.0 <=11.5.1

Published CVSS scores

4.3Mattermost, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/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.

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

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-863Incorrect Authorization
T1036Masquerading

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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