Windows Defender Zero-Days BlueHammer, RedSun, and UnDefend: Two Remain Unpatched as Active Exploitation Continues
Three Windows Defender privilege escalation zero-days — BlueHammer (CVE-2026-33825), RedSun, and UnDefend — are actively exploited in the wild. Microsoft patched BlueHammer in April 2026; RedSun and UnDefend remain unpatched. All three enable SYSTEM-level access from a low-privileged account.














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