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Critical CVE-2019-19781 Vulnerability in Citrix ADC and Gateway: Risks and Mitigations

CVE Image for report on CVE-2019-19781

Executive Summary

CVE-2019-19781 is a critical vulnerability affecting Citrix Application Delivery Controller (ADC) and Citrix Gateway (formerly known as NetScaler ADC and NetScaler Gateway). This vulnerability allows for directory traversal, which can lead to remote code execution (RCE) by unauthenticated attackers. The affected versions include Citrix ADC and Gateway 10.5, 11.1, 12.0, 12.1, and 13.0. Given the severity and the widespread use of Citrix products in various sectors, including government, healthcare, and finance, it is imperative to address this vulnerability immediately.

Technical Information

CVE-2019-19781 is a directory traversal vulnerability in Citrix ADC and Citrix Gateway. This vulnerability allows unauthenticated attackers to perform arbitrary code execution. The vulnerability is identified by the CVE ID: CVE-2019-19781 and has a CVSS v3.1 Base Score of 9.8, categorizing it as critical. The vector for this vulnerability is AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H, indicating that it can be exploited over the network, requires low attack complexity, does not require privileges or user interaction, and has a high impact on confidentiality, integrity, and availability.

The vulnerability stems from improper limitation of a pathname to a restricted directory, classified under CWE-22. This allows attackers to traverse directories and execute arbitrary code on the affected systems. The affected products include Citrix ADC and Gateway versions 10.5, 11.1, 12.0, 12.1, and 13.0.

Exploitation in the Wild

The vulnerability has been actively exploited in the wild. Attackers have been observed scanning for vulnerable Citrix ADC and Gateway instances and deploying various payloads to achieve remote code execution. Notable incidents include reports from Rapid7 and Bad Packets. Rapid7 reported active exploitation of this vulnerability shortly after its disclosure, while Bad Packets identified over 25,000 vulnerable Citrix endpoints exposed on the internet.

Specific usage of this vulnerability includes the deployment of payloads that allow attackers to gain remote access to the affected systems. Indicators of Compromise (IOCs) include unusual network traffic patterns, unexpected file modifications, and the presence of known exploit scripts on the affected systems.

APT Groups using this vulnerability

While specific APT groups exploiting this vulnerability have not been publicly identified, the ease of exploitation and the critical nature of the vulnerability make it a likely target for state-sponsored actors and organized cybercrime groups. Given the widespread use of Citrix products in critical sectors such as government, healthcare, and finance, it is plausible that APT groups targeting these sectors may leverage this vulnerability.

Affected Product Versions

The affected product versions include: - Citrix ADC and Gateway versions 10.5 - Citrix ADC and Gateway versions 11.1 - Citrix ADC and Gateway versions 12.0 - Citrix ADC and Gateway versions 12.1 - Citrix ADC and Gateway versions 13.0

Workaround and Mitigation

Citrix has released mitigation steps and patches to address this vulnerability. It is crucial to apply these updates immediately to prevent exploitation. The mitigation instructions can be found in the Citrix Support Article CTX267027 (https://support.citrix.com/article/CTX267027). Citrix has also released firmware updates for all affected versions. Organizations should prioritize applying these patches and follow the recommended mitigation steps to secure their systems.

References

For further reading and detailed technical information, please refer to the following resources: - NVD - CVE-2019-19781 (https://nvd.nist.gov/vuln/detail/CVE-2019-19781) - Citrix Blog on CVE-2019-19781 (https://www.citrix.com/blogs/2019/12/27/citrix-adc-citrix-gateway-cve-2019-19781-vulnerability/) - Rapid7 Blog on Active Exploitation (https://www.rapid7.com/blog/post/2020/01/17/active-exploitation-of-citrix-netscaler-cve-2019-19781-what-you-need-to-know/) - Bad Packets Report (https://badpackets.net/over-25000-citrix-netscaler-endpoints-vulnerable-to-cve-2019-19781/)

Rescana is here for you

At Rescana, we understand the critical importance of safeguarding your infrastructure against vulnerabilities like CVE-2019-19781. Our Continuous Threat and Exposure Management (CTEM) platform is designed to help you identify, assess, and mitigate risks in real-time. We are committed to providing you with the tools and expertise needed to protect your organization from cyber threats. If you have any questions about this report or any other issue, please do not hesitate to contact us at ops@rescana.com. We are here to assist you in securing your digital assets and ensuring the resilience of your operations.

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