Source: cret@cert.org
Belkin F9K1102 2 devices with firmware 2.10.17 use an improper algorithm for selecting the ID value in the header of a DNS query, which makes it easier for remote attackers to spoof responses by predicting this value.
Belkin F9K1102 routers with firmware 2.10.17 are vulnerable to DNS spoofing, allowing attackers to redirect network traffic. This vulnerability stems from a flawed implementation of DNS query ID selection, making it trivial for attackers to predict and forge DNS responses, potentially leading to data theft and network compromise.
Step 1: Target Identification: The attacker identifies a target network using a vulnerable Belkin F9K1102 router.
Step 2: DNS Query Observation: The attacker monitors DNS queries originating from the target network, potentially using tools like tcpdump or Wireshark.
Step 3: Query ID Prediction: The attacker analyzes the DNS query ID generation method used by the router. Due to the weak algorithm, the attacker can predict the ID for future queries.
Step 4: Crafted Response Preparation: The attacker crafts a malicious DNS response. This response includes the predicted query ID and the attacker's desired DNS record (e.g., pointing a domain to a malicious IP address).
Step 5: Response Injection: The attacker sends the crafted DNS response to the target network, attempting to deliver it before the legitimate response from the authoritative DNS server.
Step 6: Cache Poisoning: If the attacker's response arrives first, the target router and connected devices will cache the malicious DNS record.
Step 7: Traffic Redirection: Subsequent traffic destined for the spoofed domain will be redirected to the attacker's controlled server, enabling various attacks, such as phishing, malware distribution, or data exfiltration.
The vulnerability lies in the use of an improper algorithm for generating the DNS query ID. Instead of using a strong, unpredictable random number generator, the router likely uses a predictable or easily guessable method, such as a simple counter or a weak pseudo-random number generator. This allows an attacker to predict the ID used by the router when it sends a DNS query. By sending a crafted DNS response with the correct ID before the legitimate response arrives, the attacker can effectively poison the DNS cache of devices connected to the router, redirecting traffic to malicious servers. The root cause is a lack of entropy in the ID generation process, making it susceptible to brute-force attacks and response spoofing.
While specific APT groups are not directly linked to this CVE, the ease of exploitation makes it attractive to a wide range of attackers, including those involved in phishing campaigns, malware distribution, and network reconnaissance. This vulnerability could be leveraged by any actor seeking to compromise a network. CISA KEV status: Not listed.
Monitor network traffic for unusual DNS activity, such as a high volume of DNS queries or responses from unexpected sources.
Analyze DNS query and response traffic for discrepancies in IP addresses or domain name resolutions.
Use network intrusion detection systems (IDS) with rules designed to detect DNS spoofing attempts.
Examine DNS server logs for suspicious entries or changes to DNS records.
Monitor for unexpected connections to known malicious IP addresses or domains.
Upgrade the Belkin F9K1102 router firmware to a patched version (if available).
Replace the vulnerable router with a device that implements secure DNS query ID generation.
Implement DNSSEC (DNS Security Extensions) to cryptographically verify DNS responses.
Configure firewalls to restrict outbound DNS queries to trusted DNS servers.
Regularly review and update DNS records to ensure their integrity.
Educate users about the risks of phishing and other social engineering attacks.