Examining the zscaler Vulnerability
(CVE-2023-28796)
for Linux with a Pen Test Example
CVE-2023-28796 is a vulnerability found in the Zscaler Client Connector for Linux operating systems. The vulnerability is caused by the improper verification of cryptographic signatures, which allows code injection. This vulnerability affects the Zscaler Client Connector for Linux versions prior to 1.3.1.6. The severity of the vulnerability is high, with a base score of 7.8 according to the CVSS 3.x metrics.
The Zscaler Client Connector for Linux is a software that provides secure access to the Zscaler cloud security platform on Linux operating systems. It supports Zscaler Internet Access (ZIA) for both Z-Tunnel 1.0 and Z-Tunnel 2.0, as well as Zscaler Private Access (ZPA). The Zscaler Client Connector for Linux can be downloaded from the Client Connector App Store in the Zscaler Client Connector Portal.
The vulnerability in the Zscaler Client Connector for Linux allows an attacker to execute arbitrary code in the context of the current process. This could lead to a complete compromise of the system and sensitive data being stolen or modified. To mitigate the vulnerability, it is recommended to update the Zscaler Client Connector for Linux to version 1.3.1.6 or later.
Penetration testers can exploit the CVE-2023-28796 vulnerability in the Zscaler Client Connector for Linux to execute arbitrary code in the context of the current process. The following steps can be taken to demonstrate the impact of the vulnerability:
1. The penetration tester can download the vulnerable version of the Zscaler Client Connector for Linux, which is prior to version 1.3.1.6.
2. The penetration tester can create a malicious X.509 certificate and sign it with a private key.
3. The penetration tester can then use the malicious certificate to sign a malicious executable file.
4. The penetration tester can then create a malicious XE file that contains the signed malicious executable file.
5. The penetration tester can then send the malicious XE file to a victim who is using the vulnerable version of the Zscaler Client Connector for Linux.
6. When the victim opens the malicious XE file, the Zscaler Client Connector for Linux will parse the file and execute the malicious code.
7. The penetration tester can then gain access to the victim's system and steal sensitive data or modify the system.
It is important to keep the software up-to-date and to check for updates regularly to ensure the best performance and security. Zscaler recommends users apply the following mitigations to help reduce risk:
- Update Zscaler Client Connector for Linux to version 1.3.1.6 or later.
- Only open files from trusted sources.
Citations:
[1] https://en.cyberhat.online/forum/daily-cve-english/security-vulnerabilities-released-23-october-2023
[2] https://vuldb.com
[3] https://nvd.nist.gov/vuln/detail/CVE-2023-28796
[4] https://feedly.com/cve/CVE-2023-28796