CVE WatchAug 27, 2026

CVE-2021-23758

Ajax.NET Professional Deserialization of Untrusted Data Vulnerability

CVSS

8.1

High

EPSS

83.6%

p100

KEV

YES

Aug 26, 2026

Exploit Today

0-100

Published: Dec 3, 2021 · Last modified: Aug 27, 2026 · CWE-502

EPSS · 30d

83.6%EPSS · 30 days89.1%

2026-08-022026-08-30

KEV catalog record

Product

Ajax.NET Professional / Ajax.NET Professional

Vulnerability

Ajax.NET Professional Deserialization of Untrusted Data Vulnerability

Added to KEV

Aug 26, 2026

Remediate by

Sep 9, 2026

Known ransomware use

Summary description

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.

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.

Notes

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

Technical description

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.

Official references

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