CVE-2009-0758 in avahi-daemon
Summary
by MITRE
The originates_from_local_legacy_unicast_socket function in avahi-core/server.c in avahi-daemon 0.6.23 does not account for the network byte order of a port number when processing incoming multicast packets, which allows remote attackers to cause a denial of service (network bandwidth and CPU consumption) via a crafted legacy unicast mDNS query packet that triggers a multicast packet storm.
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Analysis
by VulDB Data Team • 09/01/2019
The vulnerability identified as CVE-2009-0758 affects the avahi-daemon service version 0.6.23 and resides within the avahi-core/server.c file in the originates_from_local_legacy_unicast_socket function. This flaw represents a classic network protocol implementation error that demonstrates poor handling of network byte order conversions. The issue occurs specifically when processing incoming multicast packets through legacy unicast mDNS queries, creating a scenario where remote attackers can manipulate the daemon's behavior through crafted network traffic.
The technical root cause of this vulnerability stems from the function's failure to properly convert port numbers from network byte order to host byte order before processing them. In network programming, data transmitted over networks is typically represented in network byte order, which is big-endian format, while most modern processors use little-endian byte order. When the avahi-daemon processes incoming mDNS packets, it fails to perform this crucial byte order conversion for port numbers, leading to incorrect interpretation of network data. This misinterpretation causes the daemon to treat malformed port values as valid addresses, triggering unintended network behavior.
The operational impact of this vulnerability manifests as a denial of service condition that consumes excessive network bandwidth and CPU resources. Attackers can craft malicious legacy unicast mDNS query packets that, when processed by the vulnerable daemon, initiate a multicast packet storm. This storm results in continuous network traffic generation that overwhelms the affected system's network interface and processing capabilities. The sustained high CPU utilization and bandwidth consumption effectively render the service unavailable to legitimate users while potentially affecting the entire network infrastructure that relies on multicast DNS for service discovery.
This vulnerability aligns with CWE-125: Out-of-Bounds Read and CWE-704: Incorrect Type Conversion or Cast, demonstrating how improper network byte order handling can lead to resource exhaustion and service disruption. The attack vector falls under the ATT&CK technique T1498: Network Denial of Service, specifically targeting service availability through resource exhaustion. The vulnerability's exploitability is high due to the nature of mDNS traffic being broadcast across networks, making it accessible to remote attackers without requiring privileged access. Organizations using avahi-daemon for service discovery are particularly at risk, as the vulnerability can be triggered by any device sending crafted mDNS packets to the affected system.
Mitigation strategies should focus on immediate patch deployment for avahi-daemon version 0.6.23 to address the byte order conversion issue in the origins_from_local_legacy_unicast_socket function. Network administrators should also implement ingress filtering to restrict mDNS traffic from unauthorized sources and monitor for unusual packet storm patterns. Additionally, system administrators should consider implementing rate limiting for mDNS queries and establishing proper network segmentation to contain potential exploitation attempts. The fix requires careful attention to network byte order conversion practices throughout the daemon's packet processing pipeline to prevent similar issues in other network protocol implementations.