CVE-2021-23758 Ajax.NET Professional Deserialization of Untrusted Data
Attackers can achieve remote code execution by exploiting unsafe deserialization of arbitrary .NET classes in the AjaxPro.2 library.
- Exploited in the wild
- Since 26 Aug 2026
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-23758?
CVE-2021-23758 is a high-severity unsafe deserialization vulnerability in AjaxPro.2, published on 3 Dec 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
All versions of package ajaxpro.2 are vulnerable to Deserialization of Untrusted Data due to the possibility of deserialization of arbitrary .NET classes, which can be abused to gain remote code execution.
Weakness: CWE-502
Which versions are affected by CVE-2021-23758?
2 open source packages ship an affected version, including AjaxNetProfessional. It affects 2 products.
| Package | Affected | Fixed in |
|---|---|---|
AjaxNetProfessional NuGet | All versions | 21.11.29.1 |
AjaxNetProfessional NuGet | All versions | 21.11.29.1 |
Products include Ajaxpro.2 Project Ajaxpro.2, Michaelschwarz Ajax.net Professional.
How do I fix CVE-2021-23758?
Upgrade AjaxNetProfessional to 21.11.29.1 or later. US federal agencies must fix it by 9 Sep 2026.
Upgrade, and only deserialise data from trusted sources or with an allow-list of types. More about Unsafe deserialization.
Is CVE-2021-23758 being exploited?
Yes. Attackers have exploited CVE-2021-23758 in the wild since at least 26 Aug 2026.
Public exploit code: 1 Metasploit module and 1 proofs of concept on GitHub.
Sources
Also known as GHSA-6r7c-6w96-8pvw, SNYK-DOTNET-AJAXPRO2-1925971.