What it is
CVE-2021-23758 is an unauthenticated Deserialization of Untrusted Data affecting michaelschwarz AjaxPro.2. All versions of package ajaxpro.2 are vulnerable to Deserialization of Untrusted Data due to the possibility...
Vulnerability report
Exploited in the wild
Confirmed confidence
In CISA KEV
CVE-2021-23758
Deserialization of Untrusted Data
michaelschwarz / AjaxPro.2 · affected before unspecified
- Severity
- CVSS 8.1 · High
- Confidence
- Confirmed
- Exploit status
- Exploited in the wild
- EPSS
- 89.1%
- First observed
- —
- Last observed
- —
Decision summary
What security teams need to know first
Direct answers before the deeper technical record.
Is it exploited?
Yes. Previdian tracks this CVE as a known exploited vulnerability. Confidence is confirmed. Listed in CISA KEV. Also confirmed by third-party sources.
Who is affected?
michaelschwarz / AjaxPro.2 affected before unspecified.
What should we do?
Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
Overview
Deserialization of Untrusted Data
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.
Vendor
Product
Affected
Status
n/a
AjaxPro.2
Before unspecified
Affected
- Published
- 03 Dec 2021
- Exploitation Reported
- 26 Aug 2026
- Attack vector
- Remote
- Complexity
- High
- Privileges
- None
- User interaction
- None
Tags
dotnet
cisa
CVE References
- CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2021-23758
- snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971 snyk.io · CVE Record https://snyk.io/vuln/SNYK-DOTNET-AJAXPRO2-1925971
- GitHub — michaelschwarz/Ajax.NET-Professional github.com · CVE Record https://github.com/michaelschwarz/Ajax.NET-Professional/commit/b0e63b...
- packetstormsecurity.com/files/175677/AjaxPro-Deserialization-Remote-... packetstormsecurity.com · CVE Record http://packetstormsecurity.com/files/175677/AjaxPro-Deserialization-R...
Exploitation evidence
Why Previdian marks this CVE as exploited
Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.
Exploited in the wild
CISA
Independent exploitation attestation added to the Previdian record.
Proof of concept available
GitHub
Public scanner or PoC coverage increases practical exploitability.
Known exploited vulnerability sources
Per-source evidence links for KEV attestations are available through the Previdian Pro API.
Learn about Pro API access| Source | Added |
|---|---|
| CISA First | 2026-08-26 17:00 UTC |
| CVE | 2026-08-26 18:01 UTC |
Detection
Operational artifacts and observed signals
Make the evidence actionable in scanner, SOC, and edge-control workflows.
Observed signals
- Request targets
- 0
- User-Agents
- 0
Raw values available in Pro and Enterprise.
Scanner coverage
Metasploit template detected 28 Apr 2025.
View Metasploit template (opens in new tab)Virtual patch status
No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.
Learn about virtual patches →Scanner Artifacts
Scanner and exploit-framework references linked to this CVE.
| Scanner | Reference | Detected |
|---|---|---|
| Metasploit | https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/windows/http/ajaxpro_deserialization_rce.rb | 28 Apr 2025 |
Risk and context
Severity, weaknesses, and research context
CVSS v3.1
8.1
High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
89.1%
Weaknesses
All CVSS Scores
CVSS v3.1
8.1
High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS v2.0
7.5
High
AV:N/AC:L/Au:N/C:P/I:P/A:P
Potential Proof of Concepts
These PoCs are unverified and could contain malware. Use at your own risk.
Timeline
From disclosure to observed exploitation
-
KEV confirmed by CVE
Exploitation attested by an external source
-
Added to CISA KEV
Listed in the CISA Known Exploited Vulnerabilities catalog
-
Metasploit module available
Exploit module available
-
Public PoC available
Public proof-of-concept code published
-
CVE published
Vulnerability disclosed publicly
-
CVE ID reserved
Identifier reserved by the CNA
Pro API
Automate this intelligence
Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.
- Evidence confidence and provenance
- First-party sensor telemetry
- PoC and scanner references
- Affected versions and enrichment
- Automation-ready JSON delivery
GET /api/v2/pro/kevs/CVE-2021-23758
Free JSON includes basic KEV fields{
"cve_id": "CVE-2021-23758",
"confidence": "Confirmed",
"cvss_score": 8.1,
"cvss_estimated": false,
"epss_score": 0.89096,
"exploit_status": {
"exploited_in_the_wild": true,
"active_exploitation_observed": false
},
"sensor_telemetry": { "attempts": 0, "sensors": 0 }
}Early warning alerts
Get alerts on high-impact exploitation
Receive curator-selected alerts when exploitation activity warrants attention. Each alert includes the evidence and context needed to decide what requires attention now.