Discovery of a vulnerability exploiting CVE-2024-21410.

A critical Microsoft Exchange security vulnerability was discovered on February 13, 2024. This vulnerability has a CVSS score of 9.8 and can be exploited to carry out an NTLM relay attack.

An attacker exploiting this vulnerability could authenticate as a legitimate user by using information transmitted over the network (NTLMv2 network hash).

Affected products:

The vulnerability was discovered by Microsoft teams and affects all versions of Microsoft Exchange.

Remediation:

Install the latest Microsoft Exchange update available on the Microsoft website:
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2024-21410

If the update is not possible, there is a script that can be used to temporarily patch the vulnerability. The script is available at the link above.
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