Actively exploited · Published Dec 3, 2021 · Assigned by snyk

CVE-2021-23758Deserialization of Untrusted Data

High 8.1 Exploited

In plain English

A high-severity unsafe deserialization in AjaxPro.2. Attackers are actively exploiting it in the wild (listed by CISA on August 26, 2026). The chance it is exploited in the next 30 days is estimated at 82.6% (higher than 99.7% of all known vulnerabilities). Ready-made attack tooling exists: Metasploit, public proof-of-concept code. Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.1High

Exploit odds (30 days)82.6%top 0.3% of all CVEs

Exploited in the wildYesCISA KEV since Aug 26, 2026

Attack tooling2Metasploit, Public PoC

CISA guidance

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.

Federal agencies must remediate by Sep 9, 2026.

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
NuGet	ajaxnetprofessional	21.11.29.1	GHSA-6r7c-6w96-8pvw

Affected products (as reported)

Vendor	Product	Versions
n/a	AjaxPro.2	0 – before unspecified

Weakness: CWE-502 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H