CVE-2021-23758
Ajax.NET Professional Deserialization of Untrusted Data Vulnerability - [Actively Exploited]
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.
INFO
Published Date :
Dec. 3, 2021, 8:15 p.m.
Last Modified :
Aug. 27, 2026, 4:16 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CISA KEV (Known Exploited Vulnerabilities)
For the benefit of the cybersecurity community and network defenders—and to help every organization better manage vulnerabilities and keep pace with threat activity—CISA maintains the authoritative source of vulnerabilities that have been exploited in the wild.
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.
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.
Unknown
This vulnerability affects an open-source component, third-party library, protocol, or proprietary implementation that could be used by different products. For more information, please see: https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2021-23758
Affected Products
The following products are affected by CVE-2021-23758
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 2.0 | HIGH | [email protected] | ||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | CRITICAL | [email protected] |
Public PoC/Exploit Available at Github
CVE-2021-23758 has a 4 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2021-23758.
| URL | Resource |
|---|---|
| http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-Code-Execution.html | Exploit VDB Entry |
| https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57 | Patch Third Party Advisory |
| https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971 | Third Party Advisory |
| http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-Code-Execution.html | Exploit VDB Entry |
| https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57 | Patch Third Party Advisory |
| https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971 | Third Party Advisory |
| https://blog.talosintelligence.com/uat-10147-chinese-speaking-adversary-integrates-agentic-ai-into-post-compromise-operations/ | Exploit Third Party Advisory |
| https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-23758 | US Government Resource |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2021-23758 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2021-23758
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
None
None
None
None
C# ASP.NET CSS JavaScript
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2021-23758 vulnerability anywhere in the article.
-
The Hacker News
CISA Adds Six Exploited Flaws to KEV, Including NetScaler, Linux, and SQL Server Bugs
The U.S. Cybersecurity and Infrastructure Security Agency (CISA) on Wednesday added six flaws to its Known Exploited Vulnerabilities (KEV) catalog, including a high-severity security vulnerability imp ... Read more
-
TheCyberThrone
CISA Adds Six Actively Exploited Vulnerabilities to KEV on Aug 26 2026
On August 26, 2026, the U.S. Cybersecurity and Infrastructure Security Agency (CISA) added six vulnerabilities to its Known Exploited Vulnerabilities (KEV) Catalog, citing evidence of active exploitat ... Read more
-
The Hacker News
UAT-10147 Uses AI to Scale Server Attacks, Deploys SPECTRE With EDR Bypass and Linux Rootkit
Cybersecurity researchers have disclosed details of a Chinese-speaking cybercrime group dubbed UAT-10147 that's targeting Windows and Linux web servers globally across the education, media, technology ... Read more
The following table lists the changes that have been made to the
CVE-2021-23758 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 27, 2026
Action Type Old Value New Value Changed SSVC {'id': 'CVE-2021-23758', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'active'}, {'automatable': 'no'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-08-26T17:44:04.350622Z'} {'id': 'CVE-2021-23758', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'active'}, {'automatable': 'no'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-08-26T00:00:00+00:00'} -
Modified Analysis by [email protected]
Aug. 26, 2026
Action Type Old Value New Value Changed CPE Configuration OR *cpe:2.3:a:ajaxpro.2_project:ajaxpro.2:*:*:*:*:*:.net:*:* versions up to (excluding) 21.10.30.1 OR *cpe:2.3:a:ajaxpro.2_project:ajaxpro.2:*:*:*:*:*:.net:*:* *cpe:2.3:a:michaelschwarz:ajax.net_professional:*:*:*:*:*:.net:*:* versions up to (excluding) 21.10.30.1 Added Reference Type Snyk: http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-Code-Execution.html Types: Exploit, VDB Entry Added Reference Type CISA-ADP: https://blog.talosintelligence.com/uat-10147-chinese-speaking-adversary-integrates-agentic-ai-into-post-compromise-operations/ Types: Exploit, Third Party Advisory Added Reference Type CISA-ADP: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-23758 Types: US Government Resource Added Reference Type CVE: http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-Code-Execution.html Types: Exploit, VDB Entry -
CVE CISA KEV Update by 9119a7d8-5eab-497f-8521-727c672e3725
Aug. 26, 2026
Action Type Old Value New Value Added Date Added 2026-08-26 Added Due Date 2026-08-26 Added Required Action 2026-08-26 Added Vulnerability Name 2026-08-26 -
CVE Modified by [email protected]
Aug. 26, 2026
Action Type Old Value New Value Added Reference http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-Code-Execution.html Added Reference https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57 Added Reference https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971 Removed Reference http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-Code-Execution.html Removed Reference https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57 Removed Reference https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971 Removed Reference Type https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57 Types: Patch, Third Party Advisory Removed Reference Type https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971 Types: Third Party Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 26, 2026
Action Type Old Value New Value Added CWE CWE-502 Added Reference https://blog.talosintelligence.com/uat-10147-chinese-speaking-adversary-integrates-agentic-ai-into-post-compromise-operations/ Added Reference https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-23758 Added SSVC {'id': 'CVE-2021-23758', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'active'}, {'automatable': 'no'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-08-26T17:44:04.350622Z'} -
CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Aug. 26, 2026
Action Type Old Value New Value Added Reference http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-Code-Execution.html Added Reference https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57 Added Reference https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971 Removed Reference http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-Code-Execution.html Removed Reference https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57 Removed Reference https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971 Removed Reference Type https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57 Types: Patch, Third Party Advisory Removed Reference Type https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971 Types: Third Party Advisory -
CVE Modified by [email protected]
Jun. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'n/a', 'product': 'AjaxPro.2', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': 'unspecified', 'versionType': 'custom'}]}] -
CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Nov. 21, 2024
Action Type Old Value New Value Added Reference http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-Code-Execution.html Added Reference https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57 Added Reference https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971 -
CVE Modified by [email protected]
May. 14, 2024
Action Type Old Value New Value -
CVE Modified by [email protected]
Nov. 14, 2023
Action Type Old Value New Value Added Reference Snyk http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-Code-Execution.html [No types assigned] -
Initial Analysis by [email protected]
Dec. 06, 2021
Action Type Old Value New Value Added CVSS V2 NIST (AV:N/AC:L/Au:N/C:P/I:P/A:P) Added CVSS V3.1 NIST AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Changed Reference Type https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57 No Types Assigned https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57 Patch, Third Party Advisory Changed Reference Type https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971 No Types Assigned https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971 Third Party Advisory Added CWE NIST CWE-502 Added CPE Configuration OR *cpe:2.3:a:ajaxpro.2_project:ajaxpro.2:*:*:*:*:*:.net:*:* versions up to (excluding) 21.10.30.1