Security firm Doyensec demonstrated a way to run attacker-chosen code inside a Windows VBS enclave, the isolated memory region meant to stay sealed even if the rest of the system is compromised. The target was SFAPE.dll, the component behind Enhanced Phishing Protection in Microsoft Defender SmartScreen, which stores a hashed form of the Windows sign-in password to check against unsafe text entry. The research was a lab proof of concept, not seen in real attacks, and Microsoft patched the flaw in its September 8, 2026 cumulative update.
The attack chain starts with a four-byte write that occurs when the enclave's Initialize function is called a second time, skipping an address check. Doyensec notes that calling this an arbitrary write would be an overstatement, but aimed correctly it corrupts the enclave's memory-boundary value, disabling its safety check. A timing bug in another function then enables a controlled wipe, which redirects an object lookup and eventually lets the researchers replace the enclave's code-dispatch table. The result is code execution inside the enclave, though the work did not demonstrate reading or stealing a user's password.
Microsoft rates the issue as Critical with a CVSS score of 7.8, and says it was not exploited or publicly known before the fix. The attack is local, requiring a program already running on the machine that loads the enclave, such as LSASS. The September update also ships a policy that blocks the old vulnerable enclave from loading. However, Doyensec notes that Windows still lacks a general blocklist for vulnerable enclaves, and an older Microsoft Edge enclave with a similar flaw, CVE-2023-36880, remains loadable, leaving the "bring your own vulnerable enclave" technique available. The only action is to install the update; there is no separate workaround. The source is a single article from The Hacker News, so no differing accounts exist.The JSON is valid. Ensure no markdown code block? The user asked