Technical details have surfaced regarding two patched security flaws in Microsoft Windows that, when combined, could result in remote code execution on Outlook without any user interaction. Akamai security researcher Ben Barnea discovered these vulnerabilities, CVE-2023-35384 and CVE-2023-36710, both addressed by Microsoft in August and October 2023, respectively. CVE-2023-35384 involves a bypass for a critical security flaw patched in March 2023 (CVE-2023-23397), which could lead to privilege escalation, theft of NTLM credentials, and the ability to conduct a relay attack.
The second flaw, CVE-2023-36710, affects the Audio Compression Manager (ACM) component, a legacy Windows multimedia framework used for managing audio codecs. This vulnerability is an integer overflow issue occurring when playing a WAV file. When combined with CVE-2023-35384, it enables attackers to download a custom sound file that, when autoplayed using Outlook’s reminder sound feature, leads to zero-click code execution on the victim’s machine.
Akamai’s report highlights that these vulnerabilities allow an attacker on the internet to chain them together, creating a full zero-click remote code execution exploit against Outlook clients. Organizations are advised to use microsegmentation to block outgoing SMB connections to remote public IP addresses, disable NTLM, or add users to the Protected Users security group to mitigate the risks associated with these vulnerabilities.
