A remote code execution bug in Microsoft Windows NLB affects widely used Windows servers; high-impact, enterprise-wide risk warranting broad alerting.
CVE-2026-83862
Use-after-free in Windows Network Load Balancing enables remote code execution.
Is CVE-2026-83862 being exploited?
Not confirmed. CVE-2026-83862 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 0.65% probability of exploitation in the next 30 days.
How severe is CVE-2026-83862?
CVE-2026-83862 is rated Critical with a CVSS score of 9.8. 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-2026-83862?
Yes. A fix has been recorded for CVE-2026-83862. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-83862 affect?
CVE-2026-83862 affects Microsoft Windows Network Load Balancing (NLB), Windows Server (NLB-enabled hosts). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-83862?
Deploy Microsoft's security update immediately; isolate or block NLB hosts if patching delayed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution as SYSTEM on NLB-enabled Windows hosts via crafted network traffic, enabling full system compromise.
Immediate action required
- affected>= 10.0.14393.0 and < 10.0.14393.9612
- affected>= 10.0.17763.0 and < 10.0.17763.9376
- 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.