Zero-day vulnerability in Microsoft Outlook

Information disclosure

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 - Information exposure


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.

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