CVE-2023-1981 in avahi
Summary
by MITRE • 05/26/2023
A vulnerability was found in the avahi library. This flaw allows an unprivileged user to make a dbus call, causing the avahi daemon to crash.
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Analysis
by VulDB Data Team • 08/13/2025
The vulnerability identified as CVE-2023-1981 resides within the avahi library, a widely deployed implementation of the mDNS (multicast DNS) and DNS-SD (DNS Service Discovery) protocols commonly found in Linux environments. This library facilitates network service discovery and hostname resolution across local networks, making it a critical component in many networked systems. The flaw manifests as a lack of proper input validation within the dbus communication interface that the avahi daemon utilizes for inter-process communication. When an unprivileged user executes a specific dbus call, the daemon fails to properly handle the malformed or unexpected input, leading to a crash condition that terminates the service.
This vulnerability represents a denial-of-service weakness classified under CWE-20, which describes improper input validation as a fundamental security flaw. The technical implementation of the avahi daemon demonstrates insufficient sanitization of dbus method calls, allowing malicious or unauthorized users to exploit the communication interface without requiring elevated privileges. The daemon's failure to properly validate incoming dbus parameters creates a path for arbitrary code execution within the context of the avahi service, though the immediate impact is limited to service disruption rather than privilege escalation. The flaw occurs at the protocol level where dbus messages are processed, specifically in the message handling routines that do not adequately check the integrity or expected format of incoming parameters.
The operational impact of CVE-2023-1981 extends beyond simple service interruption, as the avahi daemon typically runs with elevated privileges to manage network discovery services and may be integral to system networking functions. When the daemon crashes, it can disrupt local network service discovery, potentially affecting applications that depend on multicast DNS resolution for device identification and communication. Network administrators may experience intermittent connectivity issues or service outages in environments where avahi is heavily relied upon for automatic network configuration. This vulnerability can be exploited by any user with access to the local system or network, making it particularly concerning in multi-user environments or shared computing resources where privilege separation is not properly enforced.
Mitigation strategies for CVE-2023-1981 should focus on both immediate patching and operational hardening measures. The primary solution involves updating the avahi package to a version that includes proper input validation and sanitization for dbus method calls, which directly addresses the root cause of the vulnerability. System administrators should also implement network segmentation and access controls to limit user access to dbus interfaces, aligning with the principle of least privilege. Additional protective measures include monitoring for suspicious dbus activity and implementing intrusion detection systems that can identify malformed method calls targeting the avahi daemon. Organizations should consider disabling avahi services when not required and implementing proper service isolation through systemd or similar process management frameworks to contain potential impact. The vulnerability demonstrates the importance of validating all external inputs in daemon processes and aligns with ATT&CK technique T1499.004 which covers network disruption through service availability attacks.