A vulnerability identified as CVE-2023-20178 has been discovered in the client update process of Cisco AnyConnect Secure Mobility Client Software for Windows and Cisco Secure Client Software for Windows, allowing a local attacker with low-privilege access to potentially elevate their privileges to the SYSTEM level. This post will detail the vulnerability, the proof-of-concept code, possible exploits, and links to the original references.

Vulnerability Details

The cybersecurity community has uncovered a serious vulnerability in the update process of Cisco AnyConnect Secure Mobility Client Software for Windows and Cisco Secure Client Software for Windows. This vulnerability arises from the improper assignment of permissions to a temporary directory, created during the update process, and affects the client update process executed after a successful VPN connection is established.

Upon further investigation, it was determined that an attacker could exploit this vulnerability by exploiting a specific function of the Windows installer process. If successful, the attacker could execute code with SYSTEM-level privileges, granting them complete control over the affected system.

Proof of concept (PoC) code snippet

# Vulnerable section within the client update process
temp_dir = create_temp_directory()
set_permissions(temp_dir, "ALL")  # This line should have more restrictive permissions

# Attacker exploiting the vulnerable function
def exploit(temp_dir):
    malicious_code_path = copy_malicious_code_to(temp_dir)
    execute_windows_installer(malicious_code_path)

# Main function triggering the exploit
if __name__ == "__main__":
    temp_dir = find_vulnerable_temp_directory()
    exploit(temp_dir)

Exploit details

To exploit this vulnerability, the attacker would first need to access the target system as a low-privileged user. Once inside, the attacker could abuse the specific Windows installer function described above to take advantage of the lax permissions set by the vulnerable client update process. In doing so, they could successfully run their malicious code with the highest level of privileges (SYSTEM), effectively compromising the entire system.

Original references

1. Cisco Security Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-anyconnect-priv-esc-kYDsdX8n
2. CVE Details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-20178
3. National Vulnerability Database (NVD): https://nvd.nist.gov/vuln/detail/CVE-2023-20178

Conclusion

The discovery of CVE-2023-20178 highlights the importance of maintaining strict access controls and continuously checking for vulnerabilities in the software we use today. The vulnerability described in this post could have severe consequences for users depending on affected Cisco products, making timely updates and patches crucial.

To mitigate this vulnerability, affected users should immediately update their Cisco AnyConnect Secure Mobility Client Software for Windows and Cisco Secure Client Software for Windows to the latest version. This update should address the issue by properly setting the permissions for the temporary directory, preventing unauthorized access and exploitation.

Timeline

Published on: 06/28/2023 15:15:00 UTC
Last modified on: 07/12/2023 14:15:00 UTC