DEV-TOOLSApril 16, 20261 min read8 views

RedSun: System user access on Win 11/10 and Server with the April 2026 Update

The RedSun vulnerability exploits a logic flaw in Windows Defender's handling of cloud-tagged files, allowing attackers to overwrite system files and escalate privileges to administrative levels.

The Red Sun vulnerability repository

Now, normally I would just drop the PoC code and let people figure it out. But I can't for this one, it's way too funny. When Windows Defender realizes that a malicious file has a cloud tag, for whatever stupid and hilarious reason, the antivirus that's supposed to protect decides that it is a good idea to just rewrite the file it found again to it's original location. The PoC abuses this behaviour to overwrite system files and gain administrative privileges.

I think antimalware products are supposed to remove malicious files not be sure they are there but that's just me.

Source: Hacker News

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