#VU73511 Information disclosure in Microsoft Outlook and Microsoft Office - CVE-2023-23397

Vulnerability identifier: #VU73511

Vulnerability risk: Critical

CVSSv4.0: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:A/U:Red]

CVE-ID: CVE-2023-23397

CWE-ID: CWE-200

Exploitation vector: Network

Exploit availability: Yes

Vulnerable software:
Microsoft Outlook
Client/Desktop applications / Office applications
Microsoft Office
Client/Desktop applications / Office applications

Vendor: Microsoft

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.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Microsoft Outlook: 2013 RT Service Pack 1, 2013 Service Pack 1, 2013, 2016, 2019, 2021

Microsoft Office: 365, 2013 RT Service Pack 1 - 2013, 2016, 2019, 2021

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External links
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2023-23397
https://www.mdsec.co.uk/2023/03/exploiting-cve-2023-23397-microsoft-outlook-elevation-of-privilege-vulnerability/

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

Yes. This vulnerability is being exploited in the wild.