#Windows Encrypting File System (EFS)

**According to the CVSS metric, the attack complexity is high (AC:H). What does that mean for this vulnerability?** Successful exploitation of this vulnerability requires an attacker to prepare the target environment to improve exploit reliability.

**What is the attack vector for this vulnerability?** An attacker could cause a buffer overflow write leading to unauthenticated non-sandboxed code execution. **Does EFS need to be in use for this to be exploited?** No. EFS interfaces trigger a start to the EFS service if it isn’t already running. **How does Microsoft plan to address this vulnerability?** Microsoft is addressing the vulnerability in a phased two-part rollout. These updates address the vulnerability by modifying how EFS makes connections from client to server. For guidelines on how to manage the changes required for this vulnerability and more information on the phased rollout, see KB5009763: EFS security hardening changes in CVE-2021-43217. When the second phase of Windows updates become available in Q1 2022, customers will be notified via a revision to this security vulnerability. If you wish to be notified when these updates are released, we recommend that you register for the security notifications mailer to ...