CVE-2021-23758
What it is
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.
At a glance
- Exploitability
- Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.
- In the wild
- CISA lists this as exploited in real attacks. Treat as urgent.
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- ReservedThe CVE id was reserved by its CNA
- PublishedDisclosed publicly on CVE.org and NVD
- 2026-08-26 Exploited in the wildAdded to CISA's Known Exploited Vulnerabilities list
- Last updatedMost recent change to the record
- 2026-09-09 Remediation deadlineCISA's due date for federal agencies to fix it
Why it ranks here
- Exploited in the wild: yes, CISA lists it. This puts it above everything that is not.
- Exploit odds: 82.6% in the next 30 days (EPSS).
- Severity: 8.1 HIGH (CVSS).
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Added to CISA KEV
- 2026-08-26
- Exploit probability
- 82.6% · EPSS, next 30 days
- Weakness
- CWE-502 · Unsafe deserialization
- Record status
- Analyzed
Affected
- ajaxpro.2 Project ajaxpro.2
- Michaelschwarz ajax.net Professional < 21.10.30.1
Attack profile CVSS 3.1 · 8.1
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Raw vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Is it in your code?
Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.
Read https://cve-list.com/agent/cve/CVE-2021-23758.md and follow it. Check whether this project is affected by CVE-2021-23758. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
Fix and advisories
- https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57
- https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57
References
- http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-Code-Execution.html
- https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57
- https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971
- http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-Code-Execution.html
- https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57
- https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971
- https://blog.talosintelligence.com/uat-10147-chinese-speaking-adversary-integrates-agentic-ai-into-post-compromise-operations/
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-23758