#VU80670 Improper Authentication in Microsoft Exchange Server - CVE-2023-36757

Vulnerability identifier: #VU80670

Vulnerability risk: Medium

CVSSv4.0: 6.1 [CVSS:4.0/AV:A/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2023-36757

CWE-ID: CWE-287

Exploitation vector: Local network

Exploit availability: No

Vulnerable software:
Microsoft Exchange Server
Server applications / Mail servers

Vendor: Microsoft

Description

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

The vulnerability exists due to an error in the processing authentication requests. A remote user on the local network can obtain a victim's Net-NTLMv2 hash and perform an NTLM Relay attack against another service to authenticate as the user.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Microsoft Exchange Server: 2016 Cumulative Update 1 15.01.0396.030 - 2016 CU23 Jun23SU 15.01.2507.027, 2019 Cumulative Update 1 15.02.0330.005 - 2019 RTM 15.02.0221.012

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External links
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2023-36757
https://techcommunity.microsoft.com/t5/exchange-team-blog/released-august-2023-exchange-server-security-updates/ba-p/3892811
https://www.zerodayinitiative.com/advisories/ZDI-23-1447/

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the local network (LAN).

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.