KEV Intelligence

Vulnerability report

Active exploitation observed Confirmed confidence In CISA KEV

CVE-2023-4966

Unauthenticated sensitive information disclosure

Citrix / NetScaler ADC · affected before 8.50

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Severity
CVSS 9.4 · Critical
Confidence
Confirmed
Exploit status
Observed in sensors
EPSS
100.0%
First observed
12 Jun 2026
Last observed
14 Aug 2026

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2023-4966 is an unauthenticated Unauthenticated sensitive information disclosure affecting Citrix NetScaler ADC, NetScaler Gateway. Sensitive information disclosure in NetScaler ADC and NetScaler Gateway when...

Is it exploited?

Yes. KEV Intelligence sensors observed exploitation attempts with confirmed confidence.

Who is affected?

Citrix / NetScaler ADC affected before 8.50.

What should we do?

Patch immediately, validate internet-facing exposure, and monitor for matching requests.

Overview

Unauthenticated sensitive information disclosure

Sensitive information disclosure in NetScaler ADC and NetScaler Gateway when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA  virtual server.

Vendor Product Affected Status
Citrix NetScaler ADC Before 8.50 Affected
Citrix NetScaler ADC Before 49.15 Affected
Citrix NetScaler ADC Before 92.19 Affected
Citrix NetScaler ADC Before 37.164 Affected
Citrix NetScaler ADC Before 55.300 Affected
Citrix NetScaler ADC Before 55.300 Affected
Citrix NetScaler Gateway Before 8.50 Affected
Citrix NetScaler Gateway Before 49.15 Affected
Citrix NetScaler Gateway Before 92.19 Affected
Published
10 Oct 2023
Exploitation Reported
18 Oct 2023
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

malware nuclei_scanner cisa ransomware

CVE References

Exploitation evidence

Why KEV Intelligence 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

Recorded 18 Oct 2023

Independent exploitation attestation added to the KEV Intelligence record.

Active exploitation observed

KEV Intelligence sensor

First observed 12 Jun 2026

First-party sensor telemetry confirms matching exploitation attempts.

Used in malware

CISA

Recorded 18 Oct 2023

Malware families have been linked to exploitation of this CVE.

Proof of concept available

GitHub

Recorded 24 Oct 2023

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the KEV Intelligence Pro API.

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Source Added
CISA First 2023-10-18 00:00 UTC
The Shadowserver 2026-05-30 00:00 UTC
Tenable Blog 2026-06-02 14:20 UTC
KEV Intelligence 2026-07-07 07:59 UTC
CVE 2026-07-31 04:10 UTC

Operational indicators for this CVE are listed under Detection.

Sensor telemetry

First-party evidence of exploitation activity

Aggregate observations show the scale, recency, and distribution of activity without overstating sparse data.

9

Attempts observed

6

Unique attacker IPs

3

Attacker countries

DE · PL · US

3

Sensors observed

Exploitation attempts over the last 70 days

Daily events observed by KEV Intelligence sensors

Updated 19 Aug 2026

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11 Jun 25 Jun 9 Jul 23 Jul 19 Aug

First observed 12 Jun 2026 · Last observed 14 Aug 2026

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Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
1
User-Agents
4

Raw values available in Pro and Enterprise.

Virtual patch status

No KEV Intelligence virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

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Attacker IP Indicators

Attacker IP indicators observed · available in Pro and Enterprise.

Sensor-derived attacker IP indicators are available to Pro and Enterprise accounts under Detection and through the Pro API.

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Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner Reference Detected
Nuclei https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2023/CVE-2023-4966.yaml 25 Apr 2025

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

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

EPSS

100.0%

Weaknesses

Improper Restriction of Operations within the Bounds of a Memory Buffer CWE-119

Recent mention · Tenable Blog

Inside the customer environment: Where threat actors, vulnerabilities, and exposed assets intersect

Tenable Research has developed a graph-based model linking 600+ threat groups to real-world customer exposures. It reveals which vulnerabilities sit at the intersection of severity, active exploitation, and organizational risk.Key takeawaysThe "patch everything" strategy is...

Read full advisory

All Mentions

Recent mention · Tenable Blog

Inside the customer environment: Where threat actors, vulnerabilities, and exposed assets intersect

Tenable Blog · 27 May 2026

Tenable Research has developed a graph-based model linking 600+ threat groups to real-world customer exposures. It reveals which vulnerabilities sit at the intersection of severity, active exploitation, and organizational risk.Key takeawaysThe "patch everything" strategy is dead: Vulnerability prioritization based on exploitation risk offers a path forward. A directed graph model linking 600+ threat actors to vulnerabilities in 7,800 customer environments reveals that 68% of organizations carry at least one CVE previously exploited by a named adversary, and 321 tracked threat groups can...

Recent mention · Tenable Blog

Reducing Remediation Time Remains a Challenge: How Tenable Vulnerability Watch Can Help

Tenable Blog · 25 Apr 2025

Timely vulnerability remediation is an ongoing challenge for organizations as they struggle to prioritize the exposures that represent the greatest risk to their operations. Existing scoring systems are invaluable but can lack context. Here’s how Tenable’s Vulnerability Watch classification system can help.BackgroundOver the past six years working in Tenable’s research organization, I’ve watched known vulnerabilities and zero-day flaws plague organizations in the immediate aftermath of disclosure or even years afterwards. Following each blog post or threat report we’ve published, I kept...

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

Citrix Bleed - Leaking Session Tokens

nuclei · Created Unknown

Timeline

From disclosure to observed exploitation

  1. KEV confirmed by CVE

    Exploitation attested by an external source

  2. Public PoC available

    Public proof-of-concept code published

  3. Observed by KEV Intelligence sensors

    Evidence-backed exploitation signal

  4. Indicators of compromise added (8)

    Indicators of compromise recorded

  5. KEV confirmed by Tenable Blog

    Exploitation attested by an external source

  6. KEV confirmed by The Shadowserver

    Exploitation attested by an external source

  7. Nuclei template available

    Scanner coverage available

  8. Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  9. First public exploitation report

    Exploit observed in malware

  10. CVE published

    Vulnerability disclosed publicly

  11. 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.

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  • 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-2023-4966

Free JSON includes basic KEV fields 
{
  "cve_id": "CVE-2023-4966",
  "confidence": "Confirmed",
  "cvss_score": 9.4,
  "cvss_estimated": false,
  "epss_score": 0.99999,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": true
  },
  "sensor_telemetry": { "attempts": 9, "sensors": 3 }
}

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