Widely deployed Defender; network RCE could affect many endpoints.
CVE-2026-45584
Network remote code execution via Defender heap overflow.
Is CVE-2026-45584 being exploited?
Not confirmed. CVE-2026-45584 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 0.85% probability of exploitation in the next 30 days.
How severe is CVE-2026-45584?
CVE-2026-45584 is rated High with a CVSS score of 8.1. 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-2026-45584?
Yes. A fix has been recorded for CVE-2026-45584. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-45584 affect?
CVE-2026-45584 affects Microsoft Defender. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-45584?
Patch when released; enable automatic Defender updates.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution over the network could compromise a host and escalate control.
Patch when possible
- affected>= 1.1.0.0 and < 1.1.26040.8
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.