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Fencer Intel
medium 4.3

CVE-2026-28732 json

Slash command trigger-word update allowed command hijacking

published 5mo ago modified 26d ago also GHSA-wvcv-9xpm-7mqc , GO-2026-5726 , EUVD-2026-30760

cvss
4.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 4%
public exploits
0
none known

Summary

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

Patch / fix

  • go github.com/mattermost/mattermost/server/v8 8.0.0-20260306123948-f5fe8ded6b63, 10.11.14, 11.4.4, 11.5.2
  • go github.com/mattermost/mattermost-server 5.3.2-0.20260306123948-f5fe8ded6b63, 10.11.14+incompatible, 11.4.4+incompatible, 11.5.2+incompatible
  • Mattermost Mattermost 10.11.14, 11.4.4, 11.5.2, 11.6.0
  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

Is CVE-2026-28732 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
5mo ago

Exploit prediction

0.15% chance of exploitation in the next 30 days, higher than 4% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
GitHub 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

Affected packages

ecosystem package affected fixed in
go github.com/mattermost/mattermost/server/v8
>=11.5.0, <11.5.2
>=10.11.0, <10.11.14
>=11.4.0, <11.4.4
<8.0.0-20260306123948-f5fe8ded6b63
11.5.2
10.11.14
11.4.4
8.0.0-20260306123948-f5fe8ded6b63
go github.com/mattermost/mattermost-server
<5.3.2-0.20260306123948-f5fe8ded6b63
>=10.11.0+incompatible, <10.11.14+incompatible
>=11.4.0+incompatible, <11.4.4+incompatible
>=11.5.0+incompatible, <11.5.2+incompatible
5.3.2-0.20260306123948-f5fe8ded6b63
10.11.14+incompatible
11.4.4+incompatible
11.5.2+incompatible
go github.com/mattermost/mattermost-server/v5
all versions
 no fix listed
go github.com/mattermost/mattermost-server/v6
all versions
 no fix listed

Affected products

  • Mattermost Mattermost

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.