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Actively exploitedCVSS 8.1 · HIGH

CVE-2021-23758RCE via Deserialization in Ajax.NET Professional (AjaxPro)

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.

View on NVD

Analysis

Ajax.NET Professional (AjaxPro) presenta una vulnerabilidad de deserialización que permite la ejecución remota de código (RCE) mediante el uso de clases de .NET arbitrarias. Esta falla está siendo explotada activamente en entornos reales y el producto se encuentra actualmente en fin de vida, por lo que no recibirá parches oficiales. Se recomienda descontinuar su uso de inmediato y migrar a librerías con soporte para proteger servidores y aplicaciones backend.

Relevant roles

BackendWindowsciberseguridad

Severity

Score: 8.1(HIGH)
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
AV: NETWORK
AC: HIGH
PR: NONE
UI: NONE
S: UNCHANGED
C: HIGH
I: HIGH
A: HIGH
Weakness (CWE): CWE-502

CISA KEV

Added to KEV: 2026-08-26
Federal patch deadline: 2026-09-09
Known ransomware 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.

EPSS

Probability of exploitation (next 30 days): 0.8910 (89.1%)
Percentile: 99.8%
EPSS: 2026-08-26

Affects

ajaxpro.2_project:ajaxpro.2michaelschwarz:ajax.net_professional

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.

Published: 12/3/2021, 8:15:07 PM
Last modified: 8/26/2026, 7:43:02 PM

References

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