CVE-2023-38472 in avahi
Summary
by MITRE • 11/02/2023
A vulnerability was found in Avahi. A reachable assertion exists in the avahi_rdata_parse() function.
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Analysis
by VulDB Data Team • 06/12/2026
The vulnerability in Avahi represents a critical assertion failure within the avahi_rdata_parse() function that can be triggered through network input processing. This issue falls under the category of software fault injection where an assertion condition designed to catch programming errors becomes reachable during normal operation. The assertion failure occurs when the avahi daemon processes DNS Resource Record data, specifically during the parsing phase of DNS responses that contain malformed or unexpected data structures. This vulnerability is particularly concerning because it exists in a network service daemon that typically runs with elevated privileges and processes incoming network traffic from potentially untrusted sources. The assertion failure can lead to service termination or unexpected behavior that may be exploited to cause denial of service conditions or potentially allow further attack vectors.
The technical flaw manifests when the avahi_rdata_parse() function encounters input data that violates expected data formats or structures within DNS resource records. This function is responsible for parsing DNS response data that Avahi uses to resolve service names and network discovery information. When malformed data reaches this parsing function, the assertion condition that was intended to catch programming logic errors becomes active, causing the daemon to terminate or enter an unstable state. The assertion failure typically occurs due to improper validation of DNS record data lengths, unexpected data types, or malformed resource record structures that the function was not designed to handle gracefully. This represents a classic example of insufficient input validation and error handling in network services, where defensive programming practices fail to account for all possible malformed inputs.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the availability of network discovery services within affected systems. When the avahi daemon crashes or becomes unresponsive due to assertion failure, it affects the system's ability to perform zeroconf networking, service discovery, and network browsing functions that many applications depend upon. This can result in cascading failures where applications that rely on Avahi for service discovery stop functioning properly, affecting desktop environments, network management tools, and various networked applications that depend on multicast DNS resolution. The vulnerability is particularly dangerous in enterprise environments where Avahi is commonly used for service discovery and network management, as it can lead to widespread service disruption across multiple systems. Additionally, the crash behavior may be exploitable for remote code execution under certain conditions, though this would depend on the specific implementation details of how the assertion failure is handled within the broader application context.
Mitigation strategies for this vulnerability should focus on immediate patch application from the vendor, which typically involves updating the Avahi daemon to a version that properly handles malformed DNS data through improved input validation and graceful error handling. System administrators should implement network monitoring to detect unusual daemon behavior or crashes that may indicate exploitation attempts. The principle of least privilege should be enforced by running the Avahi daemon with minimal required permissions and ensuring that network access is properly restricted through firewall rules. Additionally, implementing intrusion detection systems that can monitor for DNS-related anomalies and malformed packets can provide early warning of potential exploitation attempts. Organizations should also consider implementing network segmentation to limit the impact of any successful exploitation attempts and ensure that Avahi service is not exposed to untrusted networks. This vulnerability aligns with CWE-617: Reachable Assertion which emphasizes the importance of defensive programming practices and proper error handling in network services. The issue may also map to ATT&CK technique T1210: Exploitation of Remote Services, where attackers may leverage service daemon vulnerabilities to gain unauthorized access or cause disruption. Regular security audits and penetration testing should be conducted to identify similar assertion-based vulnerabilities in other network services and ensure that defensive programming practices are consistently applied throughout the system architecture.