CVE-2006-2413 in GNUnet
Summary
by MITRE
GNUnet before SVN revision 2781 allows remote attackers to cause a denial of service (infinite loop and CPU consumption) via an empty UDP datagram, possibly involving FIONREAD errors.
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Analysis
by VulDB Data Team • 06/08/2017
The vulnerability identified as CVE-2006-2413 affects GNUnet software prior to SVN revision 2781, presenting a significant denial of service weakness that can be exploited remotely by attackers. This flaw manifests through the processing of empty UDP datagrams, creating conditions that lead to infinite loops and excessive CPU consumption within the affected system. The vulnerability specifically targets the network communication handling mechanisms within GNUnet's implementation, where the software fails to properly validate incoming UDP packets before processing them, particularly those that are empty or contain minimal data.
The technical root cause of this vulnerability lies in the improper handling of UDP datagram processing within GNUnet's network stack implementation. When an empty UDP datagram is received, the system enters an infinite loop during the FIONREAD ioctl operation, which is used to determine the amount of data available for reading from a socket. This condition occurs because the software does not adequately check for empty datagrams or properly handle the error conditions returned by FIONREAD operations when no data is present. The flaw essentially creates a race condition or logic error where the system continuously attempts to process what it perceives as valid data but encounters an empty packet that triggers malformed behavior in the socket handling code.
From an operational perspective, this vulnerability represents a critical security risk that can be exploited by remote attackers to consume system resources and effectively render the affected GNUnet service unavailable. The infinite loop and subsequent CPU exhaustion can lead to complete service disruption, making it particularly dangerous in environments where availability is paramount. Attackers can simply send empty UDP packets to the target system, causing the daemon to consume 100% CPU resources and potentially crash the service or make it unresponsive to legitimate requests. This type of denial of service attack is particularly insidious because it requires minimal resources to execute and can be automated to overwhelm target systems.
The vulnerability aligns with CWE-835, which specifically addresses infinite loops in software implementations, and represents a classic example of how improper input validation can lead to resource exhaustion attacks. From an attacker's perspective, this flaw maps to several ATT&CK techniques including T1499.004 for network denial of service and T1595.001 for reconnaissance through network scanning to identify vulnerable systems. The attack vector requires only basic network connectivity and does not require authentication or specialized privileges, making it accessible to a wide range of threat actors. Organizations using GNUnet should consider implementing network-level protections such as UDP filtering rules, rate limiting, and monitoring for unusual CPU consumption patterns that could indicate exploitation attempts.
Mitigation strategies for this vulnerability should include immediate patching to SVN revision 2781 or later, which contains the necessary code fixes to properly handle empty UDP datagrams and prevent the infinite loop conditions. Network administrators should implement monitoring solutions that can detect unusual CPU utilization patterns and potential denial of service attacks. Additionally, defensive measures such as implementing UDP rate limiting, connection tracking, and packet filtering rules can help reduce the attack surface. The fix typically involves adding proper validation checks for empty datagrams and ensuring that FIONREAD operations are properly handled with appropriate error checking and timeout mechanisms to prevent indefinite waiting conditions. Organizations should also consider implementing intrusion detection systems that can identify and alert on suspicious UDP traffic patterns that may indicate exploitation attempts against this specific vulnerability.