Ransomware as a service: Understanding the cybercrime gig economy and how to protect yourself
Mentions the CVE; no further detail.
CVE-2019-19781 KEVRansomwarePublic exploit Critical · 9.8 EPSS >99.9%
Citrix ADC, Gateway, and SD-WAN WANOP Appliance Code Execution Vulnerability
Citrix · Application Delivery Controller (ADC), Gateway, and SD-WAN WANOP Appliance
Summary
A directory traversal flaw, classified as improper limitation of a pathname to a restricted directory, exists in Citrix Application Delivery Controller (ADC) and Gateway appliances, and the advisory's title also covers the SD-WAN WANOP Appliance. An attacker can exploit it over the network without authentication or user interaction, with low complexity, to reach files outside the intended restricted directory.
Official description · NVD
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.
Priority scorePatchfirst’s 0 to 100 ranking. It adds points for CISA KEV listing, ransomware use, EPSS, threat reports, public exploit code and CVSS. Every CVE page shows the breakdown. Breakdown
89.9 / 100
- Exploited
- Yes, in CISA KEV
- Reports
- 8
- Tactics
- 4/15
How an attack unfolds
Based on MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. mappings. Select a step to see the evidence.Exploitation timelineDated milestones for a CVE: when it was disclosed, when exploit code became public, when exploitation was confirmed, and when threat reports named it.
First seen exploited 20 days after disclosure. Public exploit code (Metasploit) was available 10 days before disclosure.
- Public exploit codeMetasploit10 days before
- Disclosedday 0
- First seen exploitedVulnCheck KEV evidence+20 days
- First dated threat reportIntel 471+8 mo
- Added to CISA KEVknown ransomware use; EU database agrees+22 mo
CISA KEV listing is when exploitation was confirmed, not necessarily the first attack.
MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. techniques
3 TechniqueOne specific attacker behaviour in MITRE ATT&CK, such as T1190 “Exploit Public-Facing Application”. IDs with a dot, like T1059.004, are sub-techniques., grouped by TacticThe attacker’s goal at a stage of an attack in MITRE ATT&CK, such as Initial Access or Persistence. Each technique belongs to one or more tactics. in kill-chain order, 5 cited passages 3Initial AccessTA0001
External Remote Services T1133 Medium Confidence (technique links)How sure Patchfirst is that an ATT&CK technique applies to this CVE. High and medium links are shown by default; low ones come from early or generic mappings, text matching, or contradict the CVE’s details. also Persistence
MITRE CTID mapping of the KEV entry · how it is exploited
CVE-2019-19781 is exploited through directory traversal, allowing an unauthenticated attacker to execute arbitrary code on affected Citrix Netscaler Application Delivery Control (ADC).
ExecutionTA0002
Command and Scripting Interpreter T1059 Medium Confidence (technique links)How sure Patchfirst is that an ATT&CK technique applies to this CVE. High and medium links are shown by default; low ones come from early or generic mappings, text matching, or contradict the CVE’s details.
MITRE CTID mapping of the KEV entry · primary impact
DiscoveryTA0007
File and Directory Discovery T1083 Medium Confidence (technique links)How sure Patchfirst is that an ATT&CK technique applies to this CVE. High and medium links are shown by default; low ones come from early or generic mappings, text matching, or contradict the CVE’s details.
MITRE CTID mapping of the KEV entry · follow-on activity
CVE-2019-19781 enabled the actors to execute directory traversal attacks.
Lower-confidence links (2)
These come from early or generic mappings, text matching, or contradict this CVE’s details (for example a public-facing technique on a bug that needs a user to open a file). Shown for completeness.
- Exploit Public-Facing ApplicationT1190 machine-matched from report text
- Web ShellT1505.003 machine-matched from report text
Detection
1 rule for this CVE · 139 general rules for its techniquesRules for this CVE
1Sigma ruleAn open, vendor-neutral detection rule for log data. Security teams convert Sigma rules into searches for their own SIEM. that reference CVE-2019-19781 directly.- Citrix Netscaler Attack CVE-2019-19781criticaltest
General rules for this CVE’s techniques
These detect the technique in general, not this specific vulnerability.
External Remote ServicesT113320 general rules
- External Remote SMB Logon from Public IPhightest
- OpenCanary - SSH Login Attempthightest
- OpenCanary - SSH New Connection Attempthightest
- OpenCanary - Telnet Login Attempthightest
- Running Chrome VPN Extensions via the Registry 2 VPN Extensionhightest
- Unusual Child Process of dns.exehightest
- Unusual File Deletion by Dns.exehightest
- Unusual File Modification by dns.exehightest
Command and Scripting InterpreterT105995 general rules
- HackTool - Sliver C2 Implant Activity Patterncriticaltest
- Lazarus Group Activitycriticaltest
- REvil Kaseya Incident Malware Patternscriticaltest
- Turla Group Lateral Movementcriticaltest
- Windows Defender AMSI Trigger Detectedhighstable
- Windows Defender Threat Detectedhighstable
- Abusable DLL Potential Sideloading From Suspicious Locationhightest
- Add Insecure Download Source To Wingethightest
File and Directory DiscoveryT108324 general rules
- Turla Group Lateral Movementcriticaltest
- WannaCry Ransomware Activitycriticaltest
- HackTool - PCHunter Executionhightest
- PUA - Seatbelt Executionhightest
- Shell Execution GCC - Linuxhightest
- Shell Execution via Find - Linuxhightest
- Shell Execution via Flock - Linuxhightest
- Shell Execution via Nice - Linuxhightest
Sigma rules © SigmaHQ, Detection Rule License 1.1; linked, not reproduced.
What security researchers reported
Named in 8 threat reports8 reportsCISA3NCSC UK2Microsoft+2Aug 2020 – May 2022 · 6 undated
Reports are matched by finding the exact id CVE-2019-19781 in their text; nobody has reviewed the match. One passage is shown per report, at most 320 characters, linked to the original.
Prioritizing “critical” vulnerabilities: A threat intelligence perspective
In December 2019, we began to see less sophisticated threat actors share information from open source reports about CVE-2019-19781 and new forum threads started where actors sought to buy an exploit for the vulnerability.
4 passages name itOriginal (opens in a new tab) ↗
Iran-Based Threat Actor Exploits VPN Vulnerabilities
CISA Alert AA20-031A: Detecting Citrix CVE-2019-19781CISA Alert AA20-073A: Enterprise VPN SecurityCISA Alert AA20-107A: Continued Threat Actor Exploitation Post Pulse Secure VPN PatchingCISA Alert AA20-206A: Threat Actor Exploitation of F5 BIG-IP CVE-2020-5902CISA Security Tip: Securing Network Infrastructure Devices…
5 passages name itOriginal (opens in a new tab) ↗
AA20-258A: Chinese Ministry of State Security-Affiliated Cyber Threat Actor Activity
Exploited Vulnerabilities CISA Alert AA20-206A: Threat Actor Exploitation of F5 BIG-IP CVE-2020-5902 CISA Alert AA20-031A: Detecting Citrix CVE-2019-19781 CISA Alert AA20-107A: Continued Threat Actor Exploitation Post Pulse Secure VPN Patching GitHub Exploit-DB What is Mimikatz: The…
4 passages name itOriginal (opens in a new tab) ↗
Show all 8 reportsShow fewer
Nefilim Ransomware
Nefilim targets vulnerabilities such as CVE-2019-11634 and CVE-2019-19781 in Citrix gateway devices, identified in December 2019 and patched in January 2020.
AA21-200B: Chinese State-Sponsored Cyber Operations: Observed TTPs
Many exploits can be mitigated by applying available patches for vulnerabilities (such as CVE-2019-11510, CVE-2019-19781, and CVE-2020-5902) affecting external remote services.
Advisory further TTPs associated with SVR cyber actors
Mentions the CVE; no further detail.
Advisory: APT29 targets
Mentions the CVE; no further detail.
Also mentioned in 50 community threat pulses (AlienVault OTX)
Weaker evidencePulses are indicator collections that anyone can publish. A mention is not confirmation of exploitation.
- Actively_Exploited_Kev | Oct 29, 202628 Oct 2026
- Actively_Exploited_Kev | Oct 28, 202627 Oct 2026
- Actively_Exploited_Kev | Oct 27, 202626 Oct 2026
- Actively_Exploited_Kev | Oct 24, 202623 Oct 2026
- Actively_Exploited_Kev | Oct 23, 202622 Oct 2026
- Actively_Exploited_Kev | Oct 22, 202621 Oct 2026
- 44 more on OTX