CVE-2021-23758
Deserialization RCE in Ajax.NET Professional allowing remote code execution
Is CVE-2021-23758 being exploited?
Yes. CVE-2021-23758 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2021-23758?
CVE-2021-23758 is rated Critical with a CVSS score of 9.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2021-23758?
Yes. A fix has been recorded for CVE-2021-23758. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2021-23758 affect?
CVE-2021-23758 affects Ajax.NET Professional (AjaxPro), ajaxpro.2 library, Applications embedding Ajax.NET Professional. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2021-23758?
Apply vendor patch or remove/replace AjaxPro; block internet exposure; follow CISA BOD 26-04.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution on servers using Ajax.NET by deserializing arbitrary .NET classes, enabling full server compromise and lateral movement.
Immediate action required
- affected< unspecified
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.