CWE-350 Reliance on Reverse DNS Resolution for a Security-Critical Action

The product performs reverse DNS resolution on an IP address to obtain the hostname and make a security decision, but it does not properly ensure that the IP address is truly associated with the hostname.

• Access Control: Gain Privileges or Assume Identity, Bypass Protection Mechanism — Attackers can spoof DNS names by either (1) compromising a DNS server and modifying its records (sometimes called DNS cache poisoning), or (2) having legitimate control over a DNS server associated with their IP address. It may be difficult for the product to detect if a trusted DNS server has been compromised. When the product performs a reverse DNS resolution for an IP address, if an attacker controls the DNS server for that IP address, then the attacker can cause the server to return an arbitrary hostname. As a result, the attacker may be able to bypass authentication, cause the wrong hostname to be recorded in log files to hide activities, or perform other attacks.

• [Architecture and Design] Use other means of identity verification that cannot be simply spoofed. Possibilities include a username/password or certificate. • [Implementation] Perform proper forward and reverse DNS lookups to detect DNS spoofing.

• Automated Static Analysis: Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

• CVE-2001-1488: Does not do double-reverse lookup to prevent DNS spoofing. • CVE-2001-1500: Does not verify reverse-resolved hostnames in DNS. • CVE-2000-1221: Authentication bypass using spoofed reverse-resolved DNS hostnames. • CVE-2002-0804: Authentication bypass using spoofed reverse-resolved DNS hostnames. • CVE-2001-1155: Filter does not properly check the result of a reverse DNS lookup, which could allow remote attackers to bypass intended access restrictions via DNS spoofing. • CVE-2004-0892: Reverse DNS lookup used to spoof trusted content in intermediary. • CVE-2003-0981: Product records the reverse DNS name of a visitor in the logs, allowing spoofing and resultant XSS.