CVE detail
CVE-2021-23758: Ajax.NET Professional Deserialization of Untrusted Data Vulnerability
Source: CISA Known Exploited Vulnerabilities catalog · back to feed
Vendor / product
Ajax.NET Professional · Ajax.NET Professional
- Date added (KEV)
- Aug 26, 2026
- CISA due date
- Sep 09, 2026
- Ransomware campaign use
- Unknown
Required action
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
Vendor fix: Vendor patch
Scorifya interpretation
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Plain English
Technical detail
From CISA
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.
This vulnerability affects an open-source component, third-party library, protocol, or proprietary implementation that could be used by different products. For more information, please see: https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2021-23758
See what attackers can see on your domain
This vulnerability is on CISA's Known Exploited Vulnerabilities list, so it is being exploited in the wild right now. Scorifya can't test for Ajax.NET Professional directly, but in about 30 seconds it shows what your own domain exposes publicly across TLS, security headers, DNS, and cookies: the surface attackers probe first.
SOC 2 compliance
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See Scorifya Controls →References
- https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57PatchThird Party Advisory
- https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57PatchThird Party Advisory
- http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-Code-Execution.htmlExploitVDB Entry
- https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971Third Party Advisory
- http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-Code-Execution.htmlExploitVDB Entry
- https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971Third Party Advisory
- https://blog.talosintelligence.com/uat-10147-chinese-speaking-adversary-integrates-agentic-ai-into-post-compromise-operations/ExploitThird Party Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-23758US Government Resource