A proof-of-concept (PoC) exploit for a previously unknown Windows zero-day vulnerability, tracked as CVE-2021-41379, has been published by a security researcher, and if exploited, this flaw could allow an unauthorized attacker to escalate their local privileges and make themselves an administrator with full permissions. Ultimately, an attacker could exploit this vulnerability as a low-privileged user, which opens a Windows command prompt with SYSTEM privileges where any commands or scripts that the attacker enters will process and execute. This vulnerability had already been patched in Microsoft’s November 2021 patch Tuesday, however the flaw was fixed incorrectly, and security researcher Abdelhamid Naceri was able to completely take over a vulnerable system in seconds. Naceri warns that at this time there is no fix, and attempting to patch the binary manually will break the Windows installer. It is highly likely that this flaw will be correctly patched in another upcoming Microsoft patch Tuesday, and the Ankura CTAPT will publish an update when that time comes.