CVE-2021-23758: Ajax.NET Professional Deserialization of Untrusted Data Vulnerability

Critical severity, CVSS 9.8. Actively exploited: in CISA KEV since 2026-08-26. EPSS: 82.6% chance of exploitation in the next 30 days.

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.

Affected products

• ajaxpro.2 Project ajaxpro.2: any version
• Michaelschwarz Ajax.NET Professional: before 21.10.30.1 (fixed in 21.10.30.1)

Published 2021-12-03. Last modified 2026-08-27.