CriticalCVE-2019-19781

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

    Published In CISA KEV since Sources: SingCERT, CVE.org

    What is affected, what to do

    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.

    The vulnerability is being actively exploited; treat it as a priority. CISA lists it as used in ransomware campaigns. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Citrix Application Delivery Controller Firmware eq 10.5..10.5
    • Citrix Application Delivery Controller Firmware eq 11.1..11.1
    • Citrix Application Delivery Controller Firmware eq 12.0..12.0
    • Citrix Application Delivery Controller Firmware eq 12.1..12.1
    • Citrix Application Delivery Controller Firmware eq 13.0..13.0
    • Citrix Netscaler Gateway Firmware eq 10.5..10.5
    • Citrix Netscaler Gateway Firmware eq 11.1..11.1
    • Citrix Netscaler Gateway Firmware eq 12.0..12.0
    • Citrix Netscaler Gateway Firmware eq 12.1..12.1
    • Citrix Gateway Firmware eq 13.0..13.0

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    9.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: SingCERT, CVE.org

    —

    EPSS score

    No value is available for this vulnerability.

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    254.00 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploitedSource: ANSSI / CERT-FR How we classify
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    9.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.8
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 8 January 2020
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-22

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This is one of the most heavily weaponised perimeter flaws of the past years: network-reachable without authentication, trivial exploitation, code execution as nobody with a well-known path to root. CISA flags it as used in ransomware campaigns, which matches reality — several major ransomware operations relied on CVE-2019-19781 for initial access, and mass-deployed webshells such as NOTROBIN established persistent footholds. For NIS2-regulated organisations with internet-facing Citrix gateways, any still-unpatched instance should be assumed compromised; patching alone closes the front door while leaving the intruder inside the building.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Deploy vendor patches now: Citrix ADC/Gateway 13.0-47.24, 12.1-55.18, 12.0-63.21, 11.1-64.14, 10.5-70.18 and SD-WAN WANOP 10.2.6b/11.0.3b. Prioritise internet-facing appliances on TCP/443 and TCP/80.
      • If patching cannot happen inside the maintenance window, apply Citrix workaround CTX267027: responder policies that block requests containing /vpns/, /vpns/cfg/smb.conf and any path with /../, plus the documented nsapimgr flag.
      • Treat every unpatched appliance as potentially compromised. Inspect /var/tmp/netscaler/portal/templates/ and /netscaler/portal/templates/ for foreign .xml or .pl files; review /var/log/httpaccess.log and /var/log/bash.log for post-exploitation activity. The patch does not remove existing webshells.
      • Rotate every credential the appliance ever touched: local nsroot, LDAP/RADIUS bind accounts, session cookies, AD service accounts tied to the gateway. Reissue TLS server certificates if the private keys lived on the box.
      • Where compromise is suspected, take the appliance offline and rebuild from clean image — the only reliable way to remove persistence.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: move the management interface (NSIP) into a dedicated OOB VLAN, reachable only through a jump host with MFA. Never expose management on the internet.
      • Front the appliance with a WAF or reverse proxy that blocks /../, URL-encoded variants (%2e%2e%2f, %252e%252e%252f) and direct access to /vpns/ paths before traffic reaches Citrix.
      • Enable inline IPS signatures for CVE-2019-19781 (available in ET Open, Talos and Cisco rulesets for years). Block mode, not alert-only.
      • Enforce egress filtering on the appliances: restrict outbound traffic to defined backend destinations only, deny arbitrary outbound on TCP/443, TCP/4444, TCP/8080 or IRC ports — the usual C2 channels after webshell deployment.
      • Harden configuration: disable unused features (Gateway, AAA, LB vServer), rename the nsroot account, limit shell access via set system user, forward audit logs to central SIEM/syslog.
      • Lifecycle: formally decommission EOL versions (10.5); future zero-days on that line will not be fixed.

    3. Runbook step 3

      Detection rules

      • Web access logs: pattern GET /vpn/../vpns/ or POST /vpns/portal/scripts/newbm.pl in /var/log/httpaccess.log is the canonical exploit fingerprint. Sigma: selection: cs-uri-stem|contains: ['/vpns/portal/scripts/newbm.pl', '/vpn/../vpns/cfg/smb.conf'].
      • File-system monitoring (auditd/EDR): new files in /netscaler/portal/templates/ and /var/tmp/netscaler/portal/templates/, especially .xml files containing Perl backticks or print() payloads.
      • Process telemetry: child processes of httpd or nsppe spawning /bin/sh, perl, curl or wget on the appliance — base rate on a hardened ADC is zero.
      • Network telemetry (Zeek/Suricata): HTTP requests with ..%2f or ..;/ in the path hitting Citrix VIPs; outbound connections from the appliance to non-corporate IPs/domains, in particular mining pools or known C2 infrastructure.
      • SIEM hunting: KQL shape DeviceNetworkEvents | where DeviceName startswith "ns" and RemotePort in (4444, 1337, 8080) and ActionType == "ConnectionSuccess" for post-exploitation beaconing.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    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.

    Source: CSA/SingCERT, CISA KEV Catalog, cvelistv5, NVD (NIST), CVE.org (MITRE)

    Vendors and products

    Affected operating systems

    Affected operating systems
    Othercitrixapplication_delivery_controller_firmware10.5
    Othercitrixapplication_delivery_controller_firmware11.1
    Othercitrixapplication_delivery_controller_firmware12.0
    Othercitrixapplication_delivery_controller_firmware12.1
    Othercitrixapplication_delivery_controller_firmware13.0
    Othercitrixgateway_firmware13.0
    Othercitrixnetscaler_gateway_firmware10.5
    Othercitrixnetscaler_gateway_firmware11.1
    Othercitrixnetscaler_gateway_firmware12.0
    Othercitrixnetscaler_gateway_firmware12.1

    Weakness classes (CWE)

    • CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

      Base

      The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

      Entry at MITRE CWE-22

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    ANSSI / CERT-FRLicence Ouverte 2.0, as of CERTFR-2020-ALE-002 – Vulnérabilité dans les produits Citrix ADC et Citrix Gateway (clôturée 2020-07-31) (opens in a new tab)cert.cyber.gouv.fractively exploited
    Packet StormCitrix Application Delivery Controller Gateway Remote Code Execution (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormCitrix Application Delivery Controller Gateway Remote Code Execution Traversal (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormCitrix Application Delivery Controller Gateway 10.5 Remote Code Execution (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormCitrix ADC NetScaler Directory Traversal Remote Code Execution (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormCitrix ADC Gateway Path Traversal (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—

    References & sources

    • support.citrix.comarticle/CTX267027x_refsource_CONFIRM
    • kb.cert.orgVU#619785Third-party advisory, x_refsource_CERT-VN
    • twitter.combad_packets/status/1215431625766424576x_refsource_MISC
    • badpackets.netover-25000-citrix-netscaler-endpoints-vulnerable-to-cve-2019-19…x_refsource_MISC
    • forms.gleeDf3DXZAv96oosfj6x_refsource_MISC
    • packetstormsecurity.comfiles/155904/Citrix-Application-Delivery-Controller-Gateway-Rem…x_refsource_MISC
    • packetstormsecurity.comfiles/155930/Citrix-Application-Delivery-Controller-Gateway-10.…x_refsource_MISC
    • packetstormsecurity.comfiles/155905/Citrix-Application-Delivery-Controller-Gateway-Rem…x_refsource_MISC
    • packetstormsecurity.comfiles/155947/Citrix-ADC-NetScaler-Directory-Traversal-Remote-Co…x_refsource_MISC
    • packetstormsecurity.comfiles/155972/Citrix-ADC-Gateway-Path-Traversal.htmlx_refsource_MISC
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2019-19781government-resource
    • cert.cyber.gouv.frANSSI / CERT-FR: CERTFR-2020-ALE-002 – Vulnérabilité dans les produits Citrix ADC et Citrix Gateway (clôturée 2020-07-31)cert-fr
    Embed badge

    Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.

    Badge preview for CVE-2019-19781
    <a href="https://intel.neosec.eu/en/cve/CVE-2019-19781"><img src="https://intel.neosec.eu/badge/cve/CVE-2019-19781.svg?lang=en" alt="CVE-2019-19781 – NEOSEC Intel" height="20"></a>