CVE-2023-21529 Microsoft Exchange Server Deserialization of Untrusted Data
Attackers can execute arbitrary code on Microsoft Exchange Server via a deserialization vulnerability, requiring immediate patching.
- Exploited in the wild
- Since 13 Apr 2026
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2023-21529?
CVE-2023-21529 is a high-severity unsafe deserialization vulnerability in Microsoft Exchange Server, published on 14 Feb 2023. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Microsoft Exchange Server Remote Code Execution Vulnerability
Weakness: CWE-502
Which versions are affected by CVE-2023-21529?
It affects 1 product.
Products include Microsoft Exchange Server.
How do I fix CVE-2023-21529?
No fix has been published for CVE-2023-21529 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 27 Apr 2026.
Upgrade, and only deserialise data from trusted sources or with an allow-list of types. More about Unsafe deserialization.
Is CVE-2023-21529 being exploited?
Yes. Attackers have exploited CVE-2023-21529 in the wild since at least 13 Apr 2026, including in ransomware campaigns.
Other vulnerabilities in Microsoft Exchange Server
- CVE-2024-21410 Microsoft Exchange Server Privilege Escalation
- CVE-2021-34473 Microsoft Exchange Server Remote Code Execution
- CVE-2021-26855 Microsoft Exchange Server Remote Code Execution
- CVE-2021-34523 Microsoft Exchange Server Privilege Escalation
- CVE-2022-41080 Microsoft Exchange Server Privilege Escalation
Sources
Also known as GHSA-hjxr-gv9h-rjxc.