critical Known exploitedREV. 01
CVE-2021-23758Ajax.NET Professional (AjaxPro) — Untrusted Data Deserialization
The AjaxPro library for web applications deserializes untrusted request data into arbitrary server-side classes. An attacker who can reach an application built on it can run code on the server without logging in. All versions of the ajaxpro.2 package are affected.
Read the risk
THE VITAL STATS- CVSS score
- 9.8/ 10 CVSS v3.1
- EPSS probability
- 84% Likelihood of exploitation
- Attack complexity
- Low Conditions needed to exploit
- Known exploited
- Yes — CISA KEV
- CVE published
- 2021-12-03
- Added to KEV
- 2026-08-26
- Exploit published
- Yes
- Confidence
- high
- Kill chain
- initial access
- MITRE ATT&CK
- T1190, T1059
- Severity
- critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attacker needsNetwork access to a web application that exposes AjaxPro request endpoints
Behind the card
5 REFERENCES- 01CVE recordNVD recordnvd.nist.gov
- 02CISACISA Known Exploited Vulnerabilities catalogcisa.gov
- 03Vendor advisorygithub.comgithub.com
- 04Exploitpacketstormsecurity.compacketstormsecurity.com
- 05Exploitblog.talosintelligence.comblog.talosintelligence.com
Field-level provenanceTRACE THE SOURCES +
Which source supports each field, when it was retrieved, and who extracted it.
| Fields | Source | Retrieved | Extractor | Confidence |
|---|---|---|---|---|
| cvss, exploitation.attack_complexity, exploitation.exploit_available, references, published_at | nvd.nist.gov | 2026-09-21 | scrty-crds-pipeline/0.1 | high |
| exploitation.known_exploited, exploitation.kev_added | cisa.gov | 2026-09-21 | scrty-crds-pipeline/0.1 | high |
| epss | api.first.org | 2026-09-21 | scrty-crds-pipeline/0.1 | high |
| title, summary, severity, remediation, mitre_attack, kill_chain, recommended_action, confidence, tags, exploitation.prerequisites | nvd.nist.gov | 2026-09-21 | claude-code | high |
Printing history
THE RECORD- r1Initial base card
First printing. This card has not been reprinted since publication.