CVE-2026-6346
Mattermost: support packets leak plaintext credentials.
Is CVE-2026-6346 being exploited?
Not confirmed. CVE-2026-6346 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.30% probability of exploitation in the next 30 days.
How severe is CVE-2026-6346?
CVE-2026-6346 is rated High with a CVSS score of 8.7. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-6346?
Yes. A fix has been recorded for CVE-2026-6346. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-6346 affect?
CVE-2026-6346 affects Mattermost Server 10.11.x <= 10.11.13, Mattermost Server 11.4.x <= 11.4.3, Mattermost Server 11.5.x <= 11.5.1. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-6346?
Patch when available; rotate credentials; restrict support packet access.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Plaintext credentials exposed via downloadable support packets; admin or packet access can exfiltrate credentials.
Immediate action required
- affected>= 11.5.0 and <= 11.5.1
- affected>= 10.11.0 and <= 10.11.13
- affected>= 11.4.0 and <= 11.4.3
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.