Vulnerability report

Exploited in the wild Confirmed confidence In CISA KEV

CVE-2023-3519

Unauthenticated remote code execution

Citrix / NetScaler ADC · affected before 49.13

Watch CVE-2023-3519 Browse KEV feed
Severity
CVSS 9.8 · Critical
Confidence
Confirmed
Exploit status
Exploited in the wild
EPSS
99.7%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2023-3519 is an unauthenticated Unauthenticated remote code execution affecting Citrix NetScaler ADC, NetScaler Gateway.

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?

Citrix / NetScaler ADC affected before 49.13.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

Unauthenticated remote code execution

Unauthenticated remote code execution

Citrix Affected
NetScaler ADC
Before 49.13 Before 91.13 Before 37.159 Before 55.297
Citrix Affected
NetScaler Gateway
Before 49.13 Before 91.13
Published
19 Jul 2023
Exploitation Reported
19 Jul 2023
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

ransomware cisa malware metasploit nuclei_scanner

CVE References

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

Recorded 19 Jul 2023

A trusted third party reported exploitation.

Used in malware

CISA

Recorded 19 Jul 2023

Malware families have been linked to exploitation of this CVE.

Proof of concept available

GitHub

Recorded 21 Jul 2023

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 2023-07-19 00:00 UTC
The Shadowserver 2026-07-08 00:00 UTC
CVE 2026-08-05 04:30 UTC
Tenable Blog 2026-09-27 10:21 UTC

Detection

Operational artifacts and observed signals

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

Observed signals

Request targets
User-Agents
Callback hosts
0
0
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

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
Nuclei https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2023/CVE-2023-3519.yaml 01 Jun 2026
Metasploit https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/freebsd/http/citrix_formssso_target_rce.rb 28 Apr 2025

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

9.8 Critical

Potential damage if exploited. Separate from whether attackers are using it.

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

EPSS

99.7%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Improper Control of Generation of Code ('Code Injection') CWE-94

Recent mention · Tenable Blog

Frequently asked questions about reported Citrix NetScaler zero-day vulnerabilities

There are reportedly two unpatched zero-day Citrix NetScaler vulnerabilities capable of enabling remote code execution that have been actively exploited in the wild, with no patches available at this time.Key takeawaysReports indicate that there are two critical zero-day...

Read full advisory

Potential Proof of Concepts

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

Citrix NetScaler ADC and NetScaler Gateway - Remote Code Execution

nuclei · Created Unknown

citrix_formssso_target_rce

metasploit · Created Unknown

Metasploit module for CVE-2023-3519

Timeline

From disclosure to observed exploitation

  1. 10:21 UTC

    KEV confirmed by Tenable Blog

    Exploitation attested by an external source

  2. 04:30 UTC

    KEV confirmed by CVE

    Exploitation attested by an external source

  3. 00:00 UTC

    KEV confirmed by The Shadowserver

    Exploitation attested by an external source

  4. 15:34 UTC

    Nuclei template available

    Scanner coverage available

  5. 15:02 UTC

    Metasploit module available

    Exploit module available

  6. 15:02 UTC

    Public PoC available

    Public proof-of-concept code published

  7. 17:51 UTC

    CVE published

    Vulnerability disclosed publicly

  8. 00:00 UTC

    Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  9. 00:00 UTC

    First public exploitation report

    Exploit observed in malware

  10. 22:22 UTC

    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-2023-3519

Sample API response 
{
  "cve_id": "CVE-2023-3519",
  "confidence": "Confirmed",
  "cvss_score": 9.8,
  "cvss_estimated": false,
  "epss_score": 0.99749,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}