CVE-2011-1002 in avahi
Summary
by MITRE
avahi-core/socket.c in avahi-daemon in Avahi before 0.6.29 allows remote attackers to cause a denial of service (infinite loop) via an empty mDNS (1) IPv4 or (2) IPv6 UDP packet to port 5353. NOTE: this vulnerability exists because of an incorrect fix for CVE-2010-2244.
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Analysis
by VulDB Data Team • 01/16/2025
The vulnerability identified as CVE-2011-1002 affects the avahi-daemon service within the Avahi software suite, specifically targeting the avahi-core/socket.c component. This issue represents a denial of service flaw that can be exploited remotely through specially crafted mDNS packets transmitted to port 5353, which is the standard port used for Multicast DNS operations. The vulnerability emerged as an unintended consequence of a previous fix implemented for CVE-2010-2244, demonstrating how security patches can sometimes introduce new weaknesses in complex networking software. Avahi is a free software implementation of the mDNS and DNS-SD protocols that enables service discovery on local networks without requiring a traditional DNS server.
The technical flaw occurs when the avahi-daemon processes empty mDNS UDP packets sent over either IPv4 or IPv6 protocols. These packets, which contain no meaningful payload data, trigger an infinite loop within the socket processing code of the daemon. The vulnerability stems from improper handling of edge cases in packet validation logic where empty packets are not correctly identified and rejected. When the daemon receives such malformed packets, it enters a loop where it continuously processes the same empty packet without proper termination conditions, consuming excessive CPU resources and effectively rendering the service unavailable to legitimate users. This behavior constitutes a classic denial of service scenario where the system becomes unresponsive due to resource exhaustion.
The operational impact of this vulnerability extends beyond simple service disruption, as it can affect entire network environments where Avahi is deployed for service discovery. Network administrators who rely on Avahi for zero-configuration networking may experience complete loss of service discovery functionality, potentially impacting device connectivity and application availability. The vulnerability is particularly concerning because it can be exploited by any remote attacker with access to the network, requiring no authentication or specialized privileges. The infinite loop consumes system resources continuously, making it difficult to distinguish from other resource exhaustion issues and complicating troubleshooting efforts. Additionally, since this vulnerability affects the core socket handling functionality, it can potentially impact other services running on the same system that depend on proper network communication.
Mitigation strategies for CVE-2011-1002 primarily focus on updating to Avahi version 0.6.29 or later, which contains the proper fix for this issue. System administrators should also implement network-level filtering to block empty or malformed mDNS packets destined for port 5353, particularly when the service is not actively needed. Network segmentation and firewall rules can help limit exposure to unauthorized networks. The vulnerability aligns with CWE-400, which categorizes improper handling of exceptional conditions, and represents a specific instance of CWE-691, concerning inadequate control flow management. From an ATT&CK perspective, this vulnerability maps to T1499.004, which covers network denial of service attacks, and T1566.002, involving spearphishing through social engineering, as attackers may use this weakness to target network infrastructure. Organizations should also consider implementing intrusion detection systems that can identify and alert on unusual patterns of mDNS traffic that may indicate exploitation attempts, while maintaining regular patch management processes to ensure all network services remain current with security updates.