CVE-2001-0469 in rwhod
Summary
by MITRE
rwho daemon rwhod in FreeBSD 4.2 and earlier, and possibly other operating systems, allows remote attackers to cause a denial of service via malformed packets with a short length.
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Analysis
by VulDB Data Team • 02/13/2017
The rwho daemon rwhod in FreeBSD 4.2 and earlier versions contains a critical vulnerability that enables remote attackers to execute denial of service attacks through the manipulation of network packets. This vulnerability specifically targets the packet length validation mechanism within the rwhod service, which is responsible for broadcasting and receiving system information across networks. The flaw exists in the daemon's handling of incoming packets, where insufficient validation of packet headers allows malicious actors to craft specially formatted packets that trigger unexpected behavior in the service.
The technical implementation of this vulnerability stems from inadequate input validation within the rwhod daemon's packet processing routines. When the daemon receives a packet, it fails to properly verify the packet length field against expected values, creating a condition where malformed packets with shortened lengths can cause the service to crash or become unresponsive. This type of vulnerability falls under the CWE-129 weakness category, which addresses issues related to insufficient validation of length fields in input processing. The rwhod service operates on UDP port 513, making it accessible to any remote attacker who can send packets to the target system.
The operational impact of this vulnerability extends beyond simple service disruption, as it represents a fundamental flaw in the network daemon's security architecture. When exploited, the vulnerability can cause the rwhod service to terminate unexpectedly, requiring system administrators to manually restart the service or reboot the affected system. This creates a persistent denial of service condition that can be particularly problematic in environments where system availability is critical. The vulnerability also demonstrates poor defensive programming practices that align with ATT&CK technique T1499.1, which involves the exploitation of system resource exhaustion through denial of service attacks.
System administrators should implement immediate mitigations including upgrading to FreeBSD versions that contain patches for this vulnerability, which were released after version 4.2. Additionally, network-level firewalls should be configured to restrict access to the rwhod service ports, particularly when the service is not required for legitimate operations. The recommended approach involves disabling the rwhod service entirely if it is not essential for network operations, as this eliminates the attack surface entirely. Organizations should also consider implementing intrusion detection systems that can monitor for unusual packet patterns that might indicate exploitation attempts. Regular security audits should verify that all network daemons properly validate input parameters and that appropriate access controls are in place to prevent unauthorized access to system information services.