Attack Chain

1. The attacker sends a crafted GET request to the vulnerable endpoint: /api/v1/configuration/users/user-roles/user-role/rest-userrole1/web/web-bookmarks/bookmark.
2. Due to the vulnerabilities (CVE-2023-46805 and CVE-2024-21887), the authentication checks are bypassed.
3. The server processes the malicious request and attempts to access or modify web bookmark configurations.
4. Due to improper input validation, a command injection vulnerability is triggered, allowing the attacker to inject arbitrary commands.
5. The server returns a 403 Forbidden HTTP status code, indicating the request was blocked after the attempted exploitation. The response body is often empty.
6. The attacker leverages the command execution to perform reconnaissance activities, such as gathering system information using tools like uname or ipconfig.
7. The attacker attempts to establish persistence by creating new user accounts or modifying existing VPN configurations.
8. Finally, the attacker achieves their objective, which may include data exfiltration, lateral movement within the network, or deploying ransomware.

Impact

Successful exploitation of CVE-2023-46805 and CVE-2024-21887 can lead to complete compromise of the Ivanti Connect Secure VPN appliance. This can result in unauthorized access to sensitive internal resources, data breaches, and disruption of VPN services. Given that VPNs are a critical component of network security, a successful attack can have widespread consequences. The number of affected organizations is potentially very high, with victims spanning multiple sectors, including government, finance, and critical infrastructure.

Recommendation

• Deploy the Sigma rule Detect Ivanti Connect Secure Bookmark Endpoint Access to identify potential exploitation attempts based on HTTP GET requests with 403 responses targeting the specific bookmark endpoint.
• Inspect web server logs for requests matching the pattern */api/v1/configuration/users/user-roles/user-role/rest-userrole1/web/web-bookmarks/bookmark* with a 403 status code, as described in the overview.
• Investigate any alerts triggered by the provided Sigma rule or identified through manual log analysis, focusing on the source IP address (Web.src in the provided search query) and destination system (Web.dest in the provided search query).
• Apply the official patches and mitigations provided by Ivanti for CVE-2023-46805 and CVE-2024-21887 on all affected Ivanti Connect Secure VPN appliances immediately, as this is the most effective way to prevent exploitation.