Affects widely used Windows TCP/IP stack; critical LPE could disrupt many enterprises.
CVE-2026-42904
Heap overflow in Windows TCP/IP allows adjacent-network privilege escalation.
Is CVE-2026-42904 being exploited?
Not confirmed. CVE-2026-42904 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 0.44% probability of exploitation in the next 30 days.
How severe is CVE-2026-42904?
CVE-2026-42904 is rated Critical with a CVSS score of 9.6. 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-2026-42904?
Yes. A fix has been recorded for CVE-2026-42904. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-42904 affect?
CVE-2026-42904 affects Windows TCP/IP stack. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-42904?
Apply OS security updates when released; isolate affected hosts.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Attacker on same network can escalate privileges on the host via TCP/IP heap overflow.
Immediate action required
- affected>= 10.0.19044.0 and < 10.0.19044.7417
- affected>= 10.0.19045.0 and < 10.0.19045.7417
- affected>= 10.0.22631.0 and < 10.0.22631.7219
- affected>= 10.0.22631.0 and < 10.0.22631.7219
- affected>= 10.0.26100.0 and < 10.0.26100.8655
- affected>= 10.0.26200.0 and < 10.0.26200.8655
- affected>= 10.0.28000.0 and < 10.0.28000.2269
- affected>= 10.0.20348.0 and < 10.0.20348.5256
- affected>= 10.0.26100.0 and < 10.0.26100.32995
- affected>= 10.0.26100.0 and < 10.0.26100.32995
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.