CVE-2021-23758

CRITICALNVD 9.89.8—
EchelonGraph scoreHIGH confidence

Score elevated to 9.8 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2026-08-26), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 9.8 retained for reference. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: cisa_kev, epss, nvd
Trending — KEV-added this weekExploited in the wild
9.8EG
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS PROB: 84%CVSS: 9.8Exploit: cisa kev · ssvc active · Metasploit · epss top5pct · epss high · public exploitExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
9.8
EG Score
9.8(high)
EG Risk
84(Attend)
EG Risk 84/100SSVC: Attend

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation100% × 40%
Automatability0% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
84%
EPSS %ILE
100%
KEV
⚠ Exploited

Published

December 3, 2021

Last Modified

August 27, 2026

Advisory Details (5)

Auto-updated Sep 3, 2026
⚠️ Active exploitation confirmed. Patch available. Sources: github_commit, cisa.
cisa Patch Available🔴 Active Exploitation

Known Exploited Vulnerabilities Catalog | CISA

Known Exploited Vulnerabilities Catalog | CISA. Listed in CISA Known Exploited Vulnerabilities catalog.

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-23758
generic🟡 PoC Available

UAT-10147: Chinese-speaking adversary integrates agentic AI into post-compromise operations

https://blog.talosintelligence.com/uat-10147-chinese-speaking-adversary-integrates-agentic-ai-into-post-compromise-operations/
generic🔴 Active Exploitation

Deserialization of Untrusted Data in ajaxpro.2 | CVE-2021-23758 | Snyk

https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971
github_commit Patch Available

commit b0e63be5f0bb (michaelschwarz/Ajax.NET-Professional)

Patch available: michaelschwarz/Ajax.NET-Professional v21.10.30.1 (contains commit b0e63be5f0bb)

https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63be5f0bb20dfce507cb8a1a9568f6e73de57
generic

Locked Out | Packet Storm

http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-Code-Execution.html

Affected Packages

(1 across 1 ecosystem)
NuGet(1)
PackageVulnerable rangeFixed inDependents
AjaxNetProfessional21.10.30, 21.11.22, 21.11.2921.11.29.1—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 13× in last 7d / 30× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-06 13:44 UTCEPSS rescore
  2. 2026-09-06 13:44 UTCEPSS rescore
  3. 2026-09-05 16:10 UTCEG score recompute
  4. 2026-09-05 15:25 UTCEPSS rescore
  5. 2026-09-04 17:38 UTCCISA KEV update
  6. 2026-09-04 07:42 UTCEG score recompute
  7. 2026-09-04 05:03 UTCEPSS rescore
  8. 2026-09-02 17:33 UTCCISA KEV update
  9. 2026-09-01 14:28 UTCEG score recompute
  10. 2026-09-01 13:50 UTCEPSS rescore
  11. 2026-08-31 14:19 UTCCISA KEV update
  12. 2026-08-30 21:48 UTCEG score recompute
  13. 2026-08-30 19:14 UTCEPSS rescore
  14. 2026-08-29 01:07 UTCEG score recompute
  15. 2026-08-28 21:37 UTCEPSS rescore
  16. 2026-08-27 17:22 UTCCISA KEV update
  17. 2026-08-27 16:36 UTCEG score recompute
  18. 2026-08-27 14:22 UTCEPSS rescore
  19. 2026-08-26 18:22 UTCEG score recompute▲ 0.80
  20. 2026-08-26 18:20 UTCNVD updateCVSS v3 → 9.8 · severity → CRITICAL
  21. 2026-08-26 18:03 UTCEG score recompute
  22. 2026-08-26 17:41 UTCEG score recompute
  23. 2026-08-26 17:41 UTCCISA KEV update
  24. 2026-08-26 14:42 UTCEPSS rescore
  25. 2026-08-21 23:46 UTCEPSS rescore
Show 58 more
  1. 2026-08-19 14:02 UTCOSV refresh
  2. 2026-08-16 02:11 UTCEPSS rescore
  3. 2026-08-12 13:47 UTCEPSS rescore
  4. 2026-08-09 13:43 UTCEPSS rescore
  5. 2026-08-08 16:33 UTCEPSS rescore
  6. 2026-08-04 10:34 UTCEPSS rescore
  7. 2026-08-04 09:57 UTCOSV refresh
  8. 2026-08-03 10:32 UTCEPSS rescore
  9. 2026-08-01 04:12 UTCEPSS rescore
  10. 2026-07-24 14:15 UTCEPSS rescore
  11. 2026-07-23 01:57 UTCEG score recompute
  12. 2026-07-22 22:44 UTCEG score recompute
  13. 2026-07-22 14:05 UTCEPSS rescore
  14. 2026-07-20 17:04 UTCEPSS rescore
  15. 2026-07-18 06:59 UTCOSV refresh
  16. 2026-07-16 17:00 UTCEPSS rescore
  17. 2026-07-15 16:55 UTCEPSS rescore
  18. 2026-07-15 16:55 UTCEPSS rescore
  19. 2026-07-13 06:10 UTCEPSS rescore
  20. 2026-07-13 06:10 UTCEPSS rescore
  21. 2026-07-06 02:21 UTCEPSS rescore
  22. 2026-07-06 02:21 UTCEPSS rescore
  23. 2026-06-30 04:30 UTCOSV refresh
  24. 2026-06-28 04:54 UTCEPSS rescore
  25. 2026-06-28 04:54 UTCEPSS rescore
  26. 2026-06-25 13:48 UTCEPSS rescore
  27. 2026-06-25 13:48 UTCEPSS rescore
  28. 2026-06-24 14:03 UTCEPSS rescore
  29. 2026-06-24 14:03 UTCEPSS rescore
  30. 2026-06-23 21:31 UTCEPSS rescore
  31. 2026-06-23 21:31 UTCEPSS rescore
  32. 2026-06-17 17:51 UTCEPSS rescore
  33. 2026-06-15 17:46 UTCEPSS rescore
  34. 2026-06-14 23:15 UTCEPSS rescore
  35. 2026-06-12 23:10 UTCEPSS rescore
  36. 2026-06-12 23:10 UTCEPSS rescore
  37. 2026-06-12 15:40 UTCOSV refresh
  38. 2026-06-11 13:58 UTCEPSS rescore
  39. 2026-06-10 22:16 UTCEPSS rescore
  40. 2026-06-10 22:16 UTCEPSS rescore
  41. 2026-06-10 13:20 UTCEPSS rescore
  42. 2026-06-08 14:15 UTCEPSS rescore
  43. 2026-06-08 14:15 UTCEPSS rescore
  44. 2026-06-07 15:23 UTCEPSS rescore
  45. 2026-06-07 15:23 UTCEPSS rescore
  46. 2026-06-05 22:45 UTCEPSS rescore
  47. 2026-06-05 22:45 UTCEPSS rescore
  48. 2026-06-05 06:09 UTCEPSS rescore
  49. 2026-06-05 06:09 UTCEPSS rescore
  50. 2026-06-05 06:08 UTCEPSS rescore
  51. 2026-06-04 13:10 UTCEPSS rescore
  52. 2026-06-01 13:50 UTCEPSS rescore
  53. 2026-06-01 13:50 UTCEPSS rescore
  54. 2026-05-29 13:42 UTCEPSS rescore
  55. 2026-05-28 13:43 UTCEPSS rescore
  56. 2026-05-28 13:43 UTCEPSS rescore
  57. 2026-05-27 13:39 UTCEPSS rescore
  58. 2026-05-26 06:55 UTCEG score recompute

Publicly available exploits

(2 references)

Working exploit code is in the public domain (1 Metasploit module) (1 GitHub PoC). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCnumanturle/CVE-2021-23758-POC
    First seen Dec 15, 2021
    Open source ↗
  • Metasploitexploit/windows/http/ajaxpro_deserialization_rce✓ verified
    First seen Dec 3, 2021

    AjaxPro Deserialization Remote Code Execution

    Open source ↗

Related CVEs(same CWE)

Frequently asked(6)

What is CVE-2021-23758?
CVE-2021-23758 is a critical vulnerability published on December 3, 2021. 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.
When was CVE-2021-23758 disclosed?
CVE-2021-23758 was first published in the National Vulnerability Database on December 3, 2021, with the most recent update on August 27, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-23758 actively exploited?
Yes. CISA added CVE-2021-23758 to the Known Exploited Vulnerabilities catalog on August 26, 2026, affecting Ajax.NET Professional Ajax.NET Professional. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2021-23758?
CVE-2021-23758 has a CVSS v3 base score of 9.8 (NVD).
Which products are affected by CVE-2021-23758?
CVE-2021-23758 affects Ajax.NET Professional Ajax.NET Professional. The full affected-products list, including version ranges and fixed versions, is shown in the Affected Packages section of this page.
How do I remediate CVE-2021-23758?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-23758, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2021-23758

Explore →

Is Your Infrastructure Affected by CVE-2021-23758?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs