CVE-2019-19781: Citrix ADC, Gateway, and SD-WAN WANOP Appliance Code Execution Vulnerability

What it is

An issue was discovered in Citrix Application Delivery Controller (ADC) and Gateway 10.5, 11.1, 12.0, 12.1, and 13.0. They allow Directory Traversal.

Exploitation evidence

First exploit evidence seen: 2019-12-17 (earliest date across the sources below).

Exploited in the wild

• CISA KEV: listed since 2021-11-03. Source

Public exploit code

Metasploit

• auxiliary/scanner/http/citrix_dir_traversal: Citrix ADC (NetScaler) Directory Traversal Scanner (disclosure 2019-12-17)
• exploit/freebsd/http/citrix_dir_traversal_rce: Citrix ADC (NetScaler) Directory Traversal RCE (disclosure 2019-12-17)

Exploit-DB

• EDB-47901: Citrix Application Delivery Controller and Citrix Gateway - Remote Code Execution (PoC) (2020-01-11)
• EDB-47913: Citrix Application Delivery Controller and Gateway 10.5 - Remote Code Execution (Metasploit) (2020-01-13)
• EDB-47930: Citrix Application Delivery Controller (ADC) and Gateway 13.0 - Path Traversal (2020-01-16)

GitHub proof-of-concept repositories

44 public repositories from 44 accounts, first seen 2020-01-10. Most starred: trustedsec/cve-2019-19781 (573 stars), view repository.

Verify before running: public PoCs can be malicious. Read the code and only run it in an isolated lab. A PoC means exploit code is public, not that this CVE is exploited in the wild.

Sources: CISA KEV · Rapid7 Metasploit Framework module metadata · Exploit-DB (OffSec) · nomi-sec/PoC-in-GitHub.

How to fix it

CISA required action

Apply updates per vendor instructions. (source: CISA KEV)

Fixed versions

NVD does not list a fixed version for this CVE. Use the vendor advisory below.

Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.

Vendor advisories and patches

• https://support.citrix.com/article/CTX267027 (Vendor Advisory)

MITRE ATT&CK mitigations for this chain

• M1021 Restrict Web-Based Content (for T1133, T1059) : Restrict all traffic to and from public Tor nodes.
• M1030 Network Segmentation (for T1133) : Deny direct remote access to internal systems through the use of network proxies, gateways, and firewalls.
• M1042 Disable or Remove Feature or Program (for T1133, T1059) : Disable or block remotely available services that may be unnecessary.
• M1035 Limit Access to Resource Over Network (for T1133) : Limit access to remote services through centrally managed concentrators such as VPNs and other managed remote access systems.
• M1032 Multi-factor Authentication (for T1133) : Use strong two-factor or multi-factor authentication for remote service accounts to mitigate an adversary's ability to leverage stolen credentials, but be aware of [Multi-Factor Authentication Interception](https://attack.mitre.org/techniques/T1111) techniques for some two-factor authentication implementations.
• M1033 Limit Software Installation (for T1059) : Prevent user installation of unrequired command and scripting interpreters.
• M1045 Code Signing (for T1059) : Where possible, only permit execution of signed scripts.
• M1038 Execution Prevention (for T1059) : Use application control where appropriate. For example, PowerShell Constrained Language mode can be used to restrict access to sensitive or otherwise dangerous language elements such as those used to execute arbitrary Windows APIs or files (e.g., `Add-Type`).
• M1049 Antivirus/Antimalware (for T1059) : Anti-virus can be used to automatically quarantine suspicious files.
• M1026 Privileged Account Management (for T1059) : When PowerShell is necessary, consider restricting PowerShell execution policy to administrators. Be aware that there are methods of bypassing the PowerShell execution policy, depending on environment configuration. PowerShell JEA (Just Enough Administration) may also be used to sandbox administration and limit what c

Detection Generic guidance

• Initial Access: Alert on unusual requests to the affected service (odd paths, oversized payloads, exploit strings) in WAF, reverse-proxy and application logs.
• Persistence: Look for new files in web roots, new scheduled tasks/services, and new accounts created after the exposure window.
• Execution: Watch for the service process spawning shells or script interpreters (cmd.exe, powershell, sh, bash, python) via EDR process-tree rules.
• Discovery: Look for directory listing, file enumeration and reconnaissance commands from service accounts.

Response checklist Generic guidance

1. Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
2. Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
3. Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
4. Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.