What is CVE-2023-21709?

CVE-2023-21709 is a critical elevation of privilege vulnerability affecting Microsoft Exchange Server 2016 and 2019. This security issue poses a significant risk to systems running specific cumulative updates of the software. In simple terms, it allows attackers to gain unauthorized access and control over affected systems, potentially leading to severe consequences for organizations relying on these servers.

Who is impacted by this?

The CVE-2023-21709 vulnerability affects users of Microsoft Exchange Server 2016 and 2019. Specifically, impacted versions include Microsoft Exchange Server 2016 Cumulative Updates 1 to 23 and Microsoft Exchange Server 2019 Cumulative Updates 1 to 13. If you're using one of these versions and haven't applied the necessary security updates, your system may be at risk of unauthorized access and control by attackers.

What should I do if I'm affected?

If you're affected by the CVE-2023-21709 vulnerability, it's crucial to take immediate action to secure your system. Follow these simple steps to mitigate the issue:

1. Install the latest security updates for Microsoft Exchange Server 2016 or 2019, as mentioned on the Microsoft Security Update Guide.

2. Run the provided PowerShell script or command to apply the solution automatically or manually, as detailed in the Microsoft Security Update Guide.

3. Use strong passwords to protect against brute-force attacks.

Is this in CISA’s Known Exploited Vulnerabilities Catalog?

The CVE-2023-21709 vulnerability, known as Microsoft Exchange Server Elevation of Privilege Vulnerability, is not listed in CISA's Known Exploited Vulnerabilities Catalog. It was published on August 8, 2023. To address this issue, it's essential to install the security updates and follow the provided mitigation steps.

Weakness Enumeration

The weakness enumeration for this vulnerability is categorized as CWE-307, which refers to improper restriction of excessive authentication attempts.

Learn More

For a comprehensive understanding of this issue, including its description, severity, technical details, and known affected software configurations, refer to the NVD page or the sources listed below.

• Microsoft Security Update Guide

• CWE-307