Medium severity · published May 18, 2026
CVE-2026-28732
Slash command trigger-word update allowed command hijacking
4.3
CVSS
0.2%
EPSS
No
On KEV
Description
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 Fail to enforce slash command trigger-word uniqueness during command updates which allows an authenticated team member with Manage Own Slash Commands permission to hijack and impersonate existing system or custom slash commands via editing their own slash command trigger to an already-registered trigger through the command update API. Mattermost Advisory ID: MMSA-2026-00597
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
None
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 4% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MA
Mattermost · Mattermost
11.5.0 through 11.5.1; 10.11.0 through 10.11.13; 11.4.0 through 11.4.3 · source: vendor
MS
Mattermost Server · Mattermost
10.11.0 before 10.11.14; 11.4.0 before 11.4.4; 11.5.0 before 11.5.2 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-28732
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-28732
Vendor Advisory
https://mattermost.com/security-updates
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