Critical severity · published Dec 3, 2021
CVE-2021-23758
Deserialization of Untrusted Data
In wildKEV
9.8
CVSS
82.6%
EPSS
Yes
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)82.6% · higher than 100% of CVEs
Exploited in the wildYes
CISA KEVListed Aug 26, 2026
Federal remediation dueSep 9, 2026
Ransomware campaign useNot known
Affected products
Which versions
AJ
AjaxPro.2 ·
before unspecified · source: vendor, NVD
AP
Ajax.net Professional · Michaelschwarz
before 21.10.30.1 · source: NVD, KEV
In the news
AdvisoryHigh
CISA Adds Six Known Exploited Vulnerabilities to Catalog
CISA has added six new vulnerabilities to its Known Exploited Vulnerabilities (KEV) Catalog , based on evidence of active exploitation.
CVE-2015-3246 Red Hat Libuser Race Condition Vulnerability
CVE-2015-5287 Red Hat Automatic Bug Reporting Tool Privilege Escalation Vulnerability
CVE-2019-1068 Microsoft SQL Server Remote Code Execution Vulnerability
CVE-2021-23758 Ajax.NET Professional Deserialization of Untrusted Data Vulnerability
CVE-2022-0995 Linux Kernel Out-of-Bounds Write Vulnerability
CVE-2026-8452 Citrix NetScaler ADC and NetScaler Gateway Improper Restriction of Operations within the Bounds of a Memory Buffer Vulnerability
These types of vulnerabilities are a frequent attack vector for malicious cyber actors and pose significant risks to the federal enterprise.
Binding Operational Directive (BOD) 26-04: Prioritizing Security Updates Based on Risk establishes vulnerability management requirements for Federal Civilian Executive Branch (FCEB) agencies. BOD 26-04 reinforces the importance of the KEV Catalog and requires federal agencies to prioritize rapid remediation of high-risk vulnerabilities, specifically those identified by Common Vulnerabilities and Exposures (CVEs) listed in CISA’s KEV Catalog on publicly exposed assets that grant total control of the asset post-exploitation, while deferring action for lower-risk vulnerabilities. BOD 26-04 further establishes basic expectations for when agencies must check whether threat ac...
Aug 26, 2026·CISA Advisories
VulnerabilityHigh
[CISA KEV] CVE-2021-23758: Ajax.NET Professional Ajax.NET Professional - Ajax.NET Professional Deserialization of Untrusted Data Vulnerability
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.
APAjax.NET ProfessionalCVE-2021-23758
Aug 26, 2026·CISA KEV
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-23758
CVE.org
https://www.cve.org/CVERecord?id=CVE-2021-23758
CISA KEV catalogue
https://www.cisa.gov/known-exploited-vulnerabilities-catalog
Exploit
http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-Code-Execution.html
Patch
https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57
Third Party Advisory
https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971
Exploit
https://blog.talosintelligence.com/uat-10147-chinese-speaking-adversary-integrates-agentic-ai-into-post-compromise-operations/
US Government Resource
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-23758
