Citrix has released a patch fixing a remote code execution vulnerability in several versions of Netscaler ADC and Netscaler Gateway that has been exploited. Organizations are urged to patch immediately.
Background
On July 18, Citrix published a security bulletin (CTX561482) that addresses a critical remote code execution (RCE) vulnerability in Netscaler ADC (formerly known as Citrix ADC) and and Netscaler Gateway (formerly known as Citrix Gateway).
| CVE | Description | CVSSv3 | Severity |
|---|---|---|---|
| CVE-2023-3519 | Unauthenticated Remote Code Execution vulnerability | 9.8 | Critical |
In addition to CVE-2023-3519, Citrix patched two additional vulnerabilities in its ADC and Gateway appliances:
| CVE | Description | CVSSv3 | Severity |
|---|---|---|---|
| CVE-2023-3466 | Reflected Cross-Site Scripting (XSS) vulnerability | 8.3 | High |
| CVE-2023-3467 | Privilege Escalation to root administrator (nsroot) vulnerability | 8.0 | High |
Analysis
CVE-2023-3519 is a RCE vulnerability in Netscaler ADC and Netscaler Gateway. A remote, unauthenticated attacker can exploit this vulnerability to execute arbitrary code on a vulnerable server. For a target appliance to be vulnerable to exploitation, it must be configured as a Gateway (e.g. VPN, ICA Proxy, CVP, RDP Proxy) or an AAA virtual server. The vulnerability is rated as critical and Citrix reports that “Exploits of CVE-2023-3519 on unmitigated appliances have been observed.”
ADC and Gateway Historically Targeted by Attackers
Citrix’s ADC and Gateway appliances have been a valuable target for attackers in the past. For instance,in December 2022, Citrix patched another critical RCE vulnerability, CVE-2022-27518, in Citrix ADC and Gateway, that was also being exploited.
Following the disclosure of CVE-2019-19781, another unauthenticated RCE vulnerability in ADC and Gateway appliances in late 2019, active exploitation began in early 2020 and it remained a popular vulnerability with a variety of attackers including Chinese state-sponsored threat actors, Iranian-based threat actors, Russian state-sponsored threat groups as well as ransomware groups. Additionally, CVE-2019-19781 was featured as one of the Top 5 vulnerabilities in our 2020 Threat Landscape Retrospective report.
Due to the historical nature of exploitation against ADC and Gateway appliances, we strongly urge organizations to patch CVE-2023-3519 as soon as possible.
Proof of concept
At the time that this blog post was published, there was no proof-of-concept available for CVE-2023-3519.
Solution
Citrix detailed the affected and fixed versions in its security bulletin for CVE-2023-3519.
| Affected Product | Affected Version | Fixed Version |
|---|---|---|
| NetScaler ADC and NetScaler Gateway 13.1 | Before 13.1-49.13 | 13.1-49.13 and later releases |
| NetScaler ADC and NetScaler Gateway 13.0 | Before 13.0-91.13 | 13.0-91.13 and later |
| NetScaler ADC 13.1-FIPS | Before 13.1-37.159 | 13.1-37.159 and later |
| NetScaler ADC 12.1-FIPS | Before 12.1-55.297 | 12.1-55.297 and later |
| NetScaler ADC 12.1-NDcPP | Before 12.1-55.297 | 12.1-55.297 and later |
Citrix also notes that NetScaler ADC and NetScaler Gateway versions 12.1 is End of Life (EOL), and users are urged to upgrade to a supported version immediately.
Identifying affected systems
A list of Tenable plugins to identify this vulnerability will appear here as they’re released. This link uses a search filter to ensure that all matching plugin coverage will appear as it is released.
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