Zero-day vulnerability in Microsoft Outlook

Information disclosure
CVE-2023-23397

Vulnerability details

Advisory: SB2023031428 - Net-NTLMv2 hash leak in Microsoft Outlook

Vulnerable component: Microsoft Outlook

CVE-ID: CVE-2023-23397

CVSSv3 score: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N/E:H/RL:O/RC:C

CWE-ID: CWE-200 - Exposure of sensitive information to an unauthorized actor

Description:

The vulnerability allows a remote attacker to compromise the affected system.

The vulnerability exists due to the application leaks the Net-NTLMv2 hash. A remote attacker can send a specially crafted email to the victim and obtain the Net-NTLMv2 hash of the Windows account. The victim does not need to open the email, as the vulnerability is triggered automatically when it is retrieved and processed by the email server, e.g. before the email is viewed in the preview pane.

The obtained NTLMv2 hash can be used in the NTLM Relay attack against another service to authenticate as the user.

Note, the vulnerability is being actively exploited in the wild.

External links:

https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2023-23397

About zero-day vulnerabilities

Zero-day vulnerability is an undisclosed vulnerability in software that hackers can exploit to compromise computer programs, gain unauthorized access to sensitive data, penetrate networks, etc. We consider vulnerability a zero-day when there is no solution provided from software vendor and the vulnerability is being actively exploited by malicious actors.

Zero-day candidate is a potential zero-day vulnerability in software which might have been used in targeted attacks, however there is no evidence to support this suggestion.