CVE-2024-21410 is a critical security vulnerability in Microsoft Exchange Server with a CVSS severity score of 9.8. The vulnerability allows attackers to perform privilege escalation attacks by exploiting NTLM credential leaking in clients like Outlook.
Key Details
Attack Method: An attacker targets NTLM clients (like Outlook) to leak credentials, which can then be relayed against the Exchange server to gain unauthorized access and perform operations on behalf of the victim3.
Affected Systems:
- Microsoft Exchange Server 2016 Cumulative Update 23
- Microsoft Exchange Server 2019 Cumulative Update 13
- Microsoft Exchange Server 2019 Cumulative Update 14
Current Status: Microsoft has confirmed that this vulnerability is being actively exploited in the wild. In response, they have enabled Extended Protection for Authentication (EPA) by default in Exchange Server 2019 Cumulative Update 14 (CU14).
Exploit Status
Known Exploit: This vulnerability has been confirmed as actively exploited in the wild and has been added to CISA’s Known Exploited Vulnerabilities (KEV) catalog on February 15, 2024.
Public Exploit: While a public proof of concept is available, specific details about the exploitation techniques remain undisclosed. The vulnerability is actively exploited, with approximately 28,000 internet-facing Microsoft Exchange servers currently vulnerable to this exploit.
Technical Impact
The vulnerability stems from incorrect parsing of “file://” hyperlinks, which can lead to:
- NTLM credential information leakage
- Potential remote code execution
- Possible bypass of Office Protected View
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