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Fencer Vulns
high 8.1

CVE-2021-23758 kev in the critical feed json

Deserialization of Untrusted Data

published 2021-12-03 4 y ago modified 2026-08-27 2 mo ago also GHSA-6r7c-6w96-8pvw , EUVD-2021-2466

cvss
8.1
version 3.1, CNA
cisa kev
Exploited
added 2026-08-26
epss
82.6%
EPSS 82.6% chance of exploitation in 30 days, percentile 99.6%
public exploits
1
Metasploit

Summary

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.

Patch / fix

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.

  • nuget AjaxNetProfessional 21.11.29.1
  • michaelschwarz ajax.net_professional 21.10.30.1

Timeline

  1. First public exploit (Metasploit exploit/windows/http/ajaxpro_deserialization_rce)
  2. Published
  3. CISA SSVC: exploitation active
  4. Added to CISA KEV
  5. CISA patch deadline

Known exploited

Added
2 mo ago
Patch by
2026-09-09 (2 mo ago)
Ransomware
Not known
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.
Vendor, product
Ajax.NET Professional, Ajax.NET Professional
CISA name
Ajax.NET Professional Deserialization of Untrusted Data Vulnerability

CISA SSVC

Exploitation
Active, exploited in the wild
Automatable
no
Technical impact
total
Assessed
2 mo ago

Exploit prediction

82.58% chance of exploitation in the next 30 days, higher than 99.6% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

CVSS scores

assigned by version score vector
CNA 3.1 8.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P
GitHub 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
nuget AjaxNetProfessional
<21.11.29.1
21.11.29.1

Affected products

  • n/a AjaxPro.2

Classification

Weakness
  • CWE-502 Deserialization of Untrusted Data

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.