CISA KEV · Known exploitedCritical

CVE-2021-23758

AjaxPro.2, ajaxpro.2, ajax.net professional

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.

CVSS
9.8
EPSS
83.6%
99.7% percentile
CISA KEV
Listed
Published
2021.12.04
PRIORITY ASSESSMENT

Immediate action

CISA has listed this vulnerability in the Known Exploited Vulnerabilities catalog.

Known exploitationConfirmed by CISA KEV
Exploit probability83.6%
Technical severityCVSS 9.8

Vulnerability overview

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 product and versions

Product
AjaxPro.2, ajaxpro.2, ajax.net professional
Affected versions
< unspecified, < 21.10.30.1
Fixed versions
21.10.30.1

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
CISA 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.

Due date: 2026.09.09
  1. 1
    Identify

    Confirm that AjaxPro.2, ajaxpro.2, ajax.net professional and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE
CWE-502
KEV added
2026.08.26
Ransomware use
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