PatchTheCVECVE-2021-23758: Ajax.NET Professional Deserialization of Untrusted Data Vulnerability
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HIGH 8.1EXPLOITEDREMOTEMITIGATEUPGRADE
CVE-2021-23758 is a high-severity flaw (CVSS 8.1) affecting ajaxpro.2, ajax.net professional, reported as exploited in the wild. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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.
Why this priority
- High severity
- EPSS top 1%: very likely to be exploited
- Exploited in the wild (CISA KEV)
- Public exploit reference
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 8.1 (High) |
| Attack vector | Network (remote) |
| Attack complexity | High |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 82.6% (top 1%) |
| CISA exploited list | Yes, fix due 2026-09-09 |
| Weakness | CWE-502 |
| Published | 2021-12-03 |
| Last modified | 2026-08-27 |
Am I affected?
Timeline
- Published CVE record published
- Exploited Added to the CISA Known Exploited Vulnerabilities list
- Updated Record last modified
- Deadline CISA due date for US federal agencies to patch
ajaxpro.2 project ajaxpro.2 MITIGATE
Affected: all versions
Fixed in: no fixed release known
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy ajaxpro.2 || rpm -q ajaxpro.2 || ajaxpro.2 --version
No fixed or unaffected release known
Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.
michaelschwarz ajax.net professional UPGRADE
Affected: < 21.10.30.1
Fixed in: 21.10.30.1
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy ajax.net-professional || rpm -q ajax.net-professional || ajax.net-professional --version
2. UPGRADE to 21.10.30.1 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade ajax.net-professional
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade ajax.net-professional
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
Exact fixes by distribution
A distro patch exists: prefer upgrading over downgrading.
NuGet (.NET) · AjaxNetProfessional · FIXED · 21.11.29.1 · vulnerable: <= 21.11.29 · source
dotnet add package AjaxNetProfessional --version 21.11.29.1
Fedora 46 · uv · FIXED · 0.13.5-1.fc46 · FEDORA-2026-61ea5a28c6 · source
sudo dnf upgrade --advisory=FEDORA-2026-61ea5a28c6
Public exploits and detection
Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.
- GitHub PoC: numanturle/CVE-2021-23758-POC (18 stars)
- Write-up: blog.talosintelligence.com/uat-10147-chinese-speaking-adversary-integrates-agentic-ai-into
- Write-up: snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971
- Metasploit: AjaxPro Deserialization Remote Code Execution
Verify at the official source NVD · CVE Program · CISA KEV catalog · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.