Source: cret@cert.org
Cross-site request forgery (CSRF) vulnerability on ZyXEL NBG-418N devices with firmware 1.00(AADZ.3)C0 allows remote attackers to hijack the authentication of arbitrary users.
ZyXEL NBG-418N routers with firmware 1.00(AADZ.3)C0 are vulnerable to Cross-Site Request Forgery (CSRF). This allows attackers to remotely hijack user sessions and potentially gain unauthorized access to the router's configuration and network resources. Successful exploitation could lead to complete network compromise and data exfiltration.
Step 1: Victim Logged In: The victim is logged into the ZyXEL NBG-418N router's web interface. Step 2: Attacker Crafts Malicious Payload: The attacker crafts a malicious HTML page or email containing a hidden form or JavaScript that, when loaded by the victim's browser, sends a specially crafted request to the router. This request will perform an action on the router, such as changing the DNS server settings or creating a new user account. Step 3: Victim Visits Malicious Page: The victim, unaware of the malicious content, visits the attacker's webpage or opens the malicious email. Step 4: CSRF Request Execution: The victim's browser, still authenticated to the router, automatically sends the attacker's crafted request to the router. Step 5: Router Processes Malicious Request: The router, lacking CSRF protection, processes the request as if it originated from the victim. Step 6: Successful Exploitation: The attacker's desired action is executed on the router, granting the attacker control over the router's configuration and potentially the entire network.
The vulnerability stems from a lack of CSRF protection mechanisms in the web interface of the ZyXEL NBG-418N router. Specifically, the web application does not properly validate the origin of requests, allowing an attacker to craft malicious requests that are executed by a logged-in user's browser. The root cause is the absence of anti-CSRF tokens or other origin validation techniques, such as checking the Referer header or using a unique, unpredictable token for each request. This allows an attacker to trick a user into performing actions on the router's web interface without their knowledge or consent. The flaw lies in the insecure design of the web application, which trusts all incoming requests regardless of their origin.
While no specific APT groups are directly linked to this CVE, the ease of exploitation makes it attractive to various threat actors. This vulnerability could be used as an initial access vector for more sophisticated attacks. The router's compromise could be used to pivot to other systems on the network. This vulnerability is not listed on the CISA KEV at the time of this report, but it is a high-risk vulnerability due to its potential for network compromise.
Monitor network traffic for unusual HTTP requests to the router's web interface, especially those originating from external sources or unexpected internal sources.
Analyze router logs for suspicious configuration changes, such as changes to DNS settings, user accounts, or firewall rules.
Implement a web application firewall (WAF) to filter out malicious requests.
Monitor for requests lacking the proper CSRF tokens or origin headers (if the router's web interface supports these headers).
Use network intrusion detection systems (IDS) with signatures specifically designed to detect CSRF attacks against ZyXEL routers.
Upgrade the router's firmware to a patched version that addresses the CSRF vulnerability. Check the ZyXEL website for the latest firmware updates.
Implement a web application firewall (WAF) to filter out malicious requests.
Disable the router's web interface if remote access is not required. If remote access is required, restrict access to trusted IP addresses.
Educate users about the dangers of clicking on links from untrusted sources and opening suspicious emails.
Consider replacing the vulnerable router with a more secure model if no patches are available or if the vendor no longer provides support.