CVE-2021-23758: Ajaxpro.2 Project Ajaxpro.2

What is CVE-2021-23758?

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.

CVSS9.8 NVD 3.1

SeverityCRITICAL

Exploitation In the wild In CISA KEV

EPSS83% · P100

Triage statusActive Exploit

ActionPatch immediately

CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CWECWE-502

NVD published2021-12-03

NVD last modified2026-08-27

Timeline

2021-12-03Published to the U.S. National Vulnerability Database (NVD)
2026-08-26Added to the CISA Known Exploited Vulnerabilities (KEV) catalog
2026-08-27NVD record last updated
2026-08-28First covered in a defend.network daily briefing
2026-09-09CISA federal remediation deadline (BOD 22-01)

CISA Known Exploited Vulnerability

Ajax.NET Professional Deserialization of Untrusted Data Vulnerability

Added to KEV2026-08-26

Federal patch deadline2026-09-09

Known ransomware useUnknown

Affected product

Ajaxpro.2 Project Ajaxpro.2 (also: Michaelschwarz)

NVD also lists CPE entries for: Ajaxpro.2 Project Ajaxpro.2, Michaelschwarz Ajax.Net Professional

Remediation Steps

Apply the vendor security update for Ajaxpro.2 Project Ajaxpro.2 as a priority.
Restrict network exposure of the affected service to trusted sources until patched.
Review logs and detections for indicators of exploitation.
Confirm fixed versions against the official vendor advisory before deploying.

References

Referenced in our briefings & reports

Vulnerability Priority Report – Week 3 of September 2026 (September 21 – 27)
Vulnerability Priority Report – Week 2 of September 2026 (September 14 – 20)
Vulnerability Priority Report – Week 1 of September 2026 (September 7 – 13)
Vulnerability Priority Report – Week 5 of August 2026 (August 31 – September 6)
Vulnerability Priority Report – Week 4 of August 2026 (August 24 – 30)
AI agents breach Hugging Face; Next.js, PaperCut RCEs exploited; TeamPCP arrests (2026-08-28)

Browse all tracked CVEs in the defend.network CVE database →

🤖 This CVE page is generated by defend.network from NVD, CISA KEV, EPSS, and our verified daily briefings. Severity and exploitation data come from official sources; always verify remediation steps against the official vendor advisory before acting in production.