Vulnerability

CVE-2026-6046

Medium· 5.3CVSS5.3

.rules3/5

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 validate that a username returned during bot registration belongs to a bot account, which allows an unprivileged attacker to intercept private messages sent by plugins via direct message channels by pre-registering a user account with a predictable plugin bot username.. Mattermost Advisory ID: MMSA-2026-00649

Threat signal

53/100

Elevated

Severity

medium

CVSS

5.3

EPSS

—

Active

CVSS

v3.1via NVDOpen in FIRST calculator →

5.3/ 10MEDIUMCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

Attack VectorNetworkExploitable remotely over the internet — no local access needed.
Attack ComplexityHighRequires conditions outside attacker's control (race, brute-force, configuration
Privileges RequiredLowStandard user privileges sufficient.
User InteractionNoneFully automated — no victim action needed.
ScopeUnchangedImpact contained to the vulnerable component.
Confidentiality ImpactHighTotal disclosure of sensitive data.
Integrity ImpactNoneNo integrity impact.
Availability ImpactNoneNo availability impact.

EPSS

No EPSS data

FIRST.org publishes EPSS daily. Coverage isn't universal — pre-disclosure CVEs and reserved IDs don't carry an EPSS score until at least one exploitation signal lands. Score will appear within 24 hours of the next EPSS pull.

Vendor VEX

No VEX statements published for CVE-2026-6046. Vendors publish VEX (Vulnerability Exploitability eXchange) to assert per-product whether a CVE is actually exploitable in their distribution.

SSVCDefer

No exploitation, limited impact or prevalence

exploitation: none
automatable: no
impact: partial
mission: support

Lifecycle

2026-06-12Published
2026-06-12Last modified1 source

References

https://mattermost.com/security-updates

No source-event history recorded yet. New revisions will appear here as ingestors re-fetch this CVE.