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Fencer Intel
medium 4.3

CVE-2026-3433 json

Mattermost fails to scope role_updated websocket events to authorized team and channel members

published 4mo ago modified last mo. also GHSA-rp4v-qc77-phm4 , GO-2026-6286 , EUVD-2026-36498

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 7%
public exploits
0
none known

Summary

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to restrict role_updated websocket event broadcasts to members of the affected team or channel which allows an authenticated attacker with guest-level access to observe permission scheme change notifications for private teams they are not a member of via the websocket connection.. Mattermost Advisory ID: MMSA-2026-00616

Patch / fix

  • go github.com/mattermost/mattermost-server 10.11.17, 10.11.17+incompatible, 11.5.5, 11.5.5+incompatible, 11.6.1, 11.6.1+incompatible
  • go github.com/mattermost/mattermost/server/v8 8.0.0-20260504071740-9408b98025d7
  • Mattermost Mattermost 10.11.16, 10.11.17, 11.5.5, 11.6.2, 11.7.0
  • govulncheck-vulndb SLES for SAP applications 16.0, SLES 16.0 0.0.20260827T195228-160000.1.1

suse advisories SUSE-SU-2026:23625-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260827T195228-160000.1.1

opensuse advisories openSUSE-SU-2026:21761-1

Is CVE-2026-3433 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
4mo ago

Exploit prediction

0.18% chance of exploitation in the next 30 days, higher than 7% 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:L/I:N/A:N
GitHub 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem package affected fixed in
go github.com/mattermost/mattermost-server
>=11.6.0, <11.6.1
>=11.5.0, <11.5.5
>=10.11.0, <10.11.17
>=10.11.0+incompatible, <10.11.17+incompatible
>=11.5.0+incompatible, <11.5.5+incompatible
>=11.6.0+incompatible, <11.6.1+incompatible
11.6.1
11.5.5
10.11.17
10.11.17+incompatible
11.5.5+incompatible
11.6.1+incompatible
go github.com/mattermost/mattermost/server/v8
>=8.0.0-20250731163400-5b955468ea1e, <8.0.0-20260504071740-9408b98025d7
8.0.0-20260504071740-9408b98025d7
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
  • CWE-200 Exposure of Sensitive Information to an Unauthorized Actor

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.