CVE entry · CVE-2021-23758
CVE-2021-23758: Ajax.NET Professional Deserialization of Untrusted Data Vulnerability
Ajax.NET Professional (AjaxPro) contains a deserialization of untrusted data vulnerability that could allow for remote code execution via arbitrary .NET classes. The impacted product(s) could be end-of-life (EoL) and/or end-of-service (EoS). Users are advised to discontinue use and/or transition to a supported version.
- Actively exploited: added to CISA’s KEV catalog on August 26, 2026.
- Use by ransomware: not established so far.
- Remediation deadline for US federal agencies: September 9, 2026.
Description from CISA’s KEV catalog.
What to do
- Check whether your estate includes Ajax.NET Professional, including internet-facing devices.
- Apply the vendor’s patch or mitigations (references below). Failing that, isolate the product or stop using it, as CISA requires of US federal agencies.
- An exploited vulnerability has often been used before it was fixed: look for signs of compromise, especially on internet-facing devices.