Windows SMB Client is a core, widely deployed OS component; a networkable privilege-escalation bug can broadly disrupt enterprise environments and warrants org-wide attention.
CVE-2026-83789
Heap overflow in Windows SMB Client enabling remote privilege escalation
Is CVE-2026-83789 being exploited?
Not confirmed. CVE-2026-83789 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.
How severe is CVE-2026-83789?
CVE-2026-83789 is rated High with a CVSS score of 8.8. 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-2026-83789?
Yes. A fix has been recorded for CVE-2026-83789. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-83789 affect?
CVE-2026-83789 affects Windows SMB Client, Microsoft Windows 10, Microsoft Windows 11, Windows Server (various). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-83789?
Apply Microsoft updates immediately; restrict SMB exposure and monitor SMB logs.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote, network-based privilege escalation via SMB heap overflow allowing escalation to SYSTEM or high privileges and potential code execution.
Immediate action required
- affected>= 10.0.14393.0 and < 10.0.14393.9612
- affected>= 10.0.17763.0 and < 10.0.17763.9376
- affected>= 10.0.19044.0 and < 10.0.19044.7807
- affected>= 10.0.19045.0 and < 10.0.19044.7807
- affected>= 10.0.22631.0 and < 10.0.22631.7652
- affected>= 10.0.22631.0 and < 10.0.22631.7652
- affected>= 10.0.26100.0 and < 10.0.26100.9711
- affected>= 10.0.26200.0 and < 10.0.26200.9711
- affected>= 10.0.28000.0 and < 10.0.28000.3231
- affected>= 10.0.26300.0 and < 10.0.26300.9711
- affected>= 6.2.9200.0 and < 6.2.9200.26434
- affected>= 6.3.9600.0 and < 6.3.9600.23470
- affected>= 6.3.9600.0 and < 6.3.9600.23470
- affected>= 6.2.9200.0 and < 6.2.9200.26434
- affected>= 10.0.14393.0 and < 10.0.14393.9612
- affected>= 10.0.14393.0 and < 10.0.14393.9612
- affected>= 10.0.17763.0 and < 10.0.17763.9376
- affected>= 10.0.17763.0 and < 10.0.17763.9376
- affected>= 10.0.20348.0 and < 10.0.20348.5761
- affected>= 10.0.26100.0 and < 10.0.26100.33650
- affected>= 10.0.26100.0 and < 10.0.26100.33650
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.