Remote Code Execution in AjaxNetProfessional

Exploitation

Confirmed: listed in the CISA Known Exploited Vulnerabilities catalog.

CVSS

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

EPSS

• CVE-2021-23758: 82.58% estimated exploitation activity in the next 30 days; percentile 99.67 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Overview Affected versions of this package 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. Description Serialization is a process of converting an object into a sequence of bytes which can be persisted to a disk or database or can be sent through streams. The reverse process of creating object from sequence of bytes is called deserialization. Serialization is commonly used for communication (sharing objects between multiple hosts) and persistence (store the object state in a file or a database). It is an integral part of popular protocols like Remote Method Invocation (RMI), Java Management Extension (JMX), Java Messaging System (JMS), Action Message Format (AMF), Java Server Faces (JSF) ViewState, etc. Deserialization of untrusted data (CWE-502), is when the application deserializes untrusted data without sufficiently verifying that the resulting data will be…

Published by the source

7 Dec 2021, 21:21 UTC

Last modified by the source

3 Feb 2026, 17:39 UTC

Source last checked

26 Oct 2026, 17:04 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-6r7c-6w96-8pvw

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# Patch Next advisory brief: CVE-2021-23758

Advisory: Remote Code Execution in AjaxNetProfessional
IDs: CVE-2021-23758, GHSA-6r7c-6w96-8pvw
Record: https://patchnext.com/advisories/cve-2021-23758 (revision 1, source checked 26 Oct 2026, 17:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: confirmed: listed in the CISA Known Exploited Vulnerabilities catalog.
Vendor response: Vendor fix available; fixed versions by package: ajaxnetprofessional 21.11.29.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet ajaxnetprofessional: affected <= 21.11.29; fixed in 21.11.29.1

## Suggested inspection (read-only)
- NuGet ajaxnetprofessional: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on ajaxnetprofessional.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (CISA added CVE-2021-23758 to the Known Exploited Vulnerabilities catalog on 2026-08-26.)
- Verified: https://github.com/advisories/GHSA-6r7c-6w96-8pvw (GitHub-reviewed advisory GHSA-6r7c-6w96-8pvw lists affected ranges: NuGet ajaxnetprofessional >=0 <=21.11.29)

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