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CVE-2021-23758

HIGH 8.1 KNOWN EXPLOITED PoC CATALOGUED ALL-YEARS

Published 2021-12-03 · Last modified 2026-08-27 · snyk · NVD: Analyzed

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.

ACTIVELY EXPLOITED

Confirmed exploited in the wild — in CISA KEV since 2026-08-26. Patch or mitigate now.

Exploitation likelihood

82.6%chance of exploitation in 30 days · 100th percentile

● In CISA KEV (2026-08-26)● Catalogued PoC◆ SSVC: exploitation active, automatable no

Impact if exploited

8.1CVSS 3.1 · HIGH · CNA

  • ConfidentialityHigh
  • IntegrityHigh
  • AvailabilityHigh

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ✓Privileges: No account or privileges required
  • ✓User interaction: No user interaction needed
  • ⚠Complexity: Needs a race window or specific setup

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept

Public PoC or exploit resources are catalogued below.

Listed by the named source; Vulnpedia has not tested these resources.

PoC data: JSON

Resource commands

curl -s https://vulnpedia.com/cve/CVE-2021-23758/poc.jsonMachine-readable PoC index for this CVE (for automation).

Search for new PoCs

Search GitHub now — results may be empty or unverified.

Tracked sources are checked weekly for the full archive, including PoCs published after the original disclosure. A later release appears after a tracked source lists it and a refresh succeeds.

Data snapshot:

Affected

Vendors Ajaxpro.2 Project Michaelschwarz

Products Ajaxpro.2 Ajax.Net Professional

Weakness (CWE)

  • CWE-502: Deserialization of Untrusted Data

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

References and research data (JSON)

Packages and version ranges

Each advisory describes its own package and affected ranges. A boundary applies to that range; it is not a universal upgrade recommendation.

  • AjaxNetProfessional NuGet

    pkg:nuget/AjaxNetProfessional

    ECOSYSTEM range
    • All earlier versions (introduced 0)
    • Fixed boundary (excluded): 21.11.29.1
    3 explicitly listed affected versions

    21.10.30, 21.11.22, 21.11.29

    Additional upstream package constraints
    {
  "database": {
    "last_known_affected_version_range": "<= 21.11.29",
    "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2021/12/GHSA-6r7c-6w96-8pvw/GHSA-6r7c-6w96-8pvw.json"
  }
}
    GitHub Advisory Database · GHSA-6r7c-6w96-8pvw · Updated 2026-07-08T06:49:48.183671773Z

Unverified PoC candidates

Catalogue matches for further research. These repositories have not been validated as working exploits.

1 candidate

Additional exploitation reports

Source-specific reports, separate from CISA KEV. Repeated observations from one source are not independent confirmations.

  • VulnCheck KEV · 2026-08-20T00:00:00Z

    Source guidance: 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.

    Source ransomware assessment: Unknown

    VulnCheck KEV · CVE-2021-23758 · Updated 2026-08-20T00:00:00Z
  • VulnCheck KEV · 2026-08-20T00:00:00ZVulnCheck KEV · CVE-2021-23758
  • VulnCheck KEV · 2026-08-26T00:00:00ZVulnCheck KEV · CVE-2021-23758
    VulnCheck KEV · CVE-2021-23758
  • VulnCheck KEV · 2026-09-08T00:00:00ZVulnCheck KEV · CVE-2021-23758

Known Affected Software Configurations

VendorProductVersion range
Ajaxpro.2 ProjectAjaxpro.2*
MichaelschwarzAjax.Net Professional< 21.10.30.1

All CVSS metrics

  • HIGH 8.1 v3.1 · CNA Primary
    CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
  • HIGH 8.1 v3.1 · NVD Secondary
    CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
  • CRITICAL 9.8 v3.1 · NVD Primary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  • HIGH 7.5 v2.0 · NVD Primary
    AV:N/AC:L/Au:N/C:P/I:P/A:P

References

Exploit-tagged references (not proof of a PoC)

Patches & mitigations

Advisories

Technical & other

Sources: NVD · CVE.org · All sources and attribution · EPSS