Avahi, a local service discovery daemon using mDNS/DNS‑SD, contains a reachable assertion bug in the function `transport_flags_from_domain()`. When an unprivileged local user sends a D‑Bus method call with conflicting publish flags, the assertion fails and the daemon crashes. The failure is a pure denial of service that does not provide confidentiality or integrity compromise, but it can interrupt automated service discovery and related applications. The weakness corresponds to CWE‑1288 (Asserted Condition is Not Checked) and CWE‑617 (Reachable Assertion).

The vulnerability affects the Avahi project, specifically any occurrence of the Avahi library or daemon before the 0.9‑rc4 release. Known affected builds include the 0.9‑rc1, 0.9‑rc2, and 0.9‑rc3 releases. Systems running earlier versions or these release candidates are at risk unless patched.

The CVSS v3.1 score of 5.5 indicates a moderate severity. The EPSS score is less than 1%, suggesting a low probability of exploitation under normal circumstances. The issue is not listed in the CISA Known Exploited Vulnerabilities catalog. The attack vector requires local privilege; the user must be able to interact with the avahi‑daemon's D‑Bus interface. Exploitation does not depend on network connectivity and can be performed by any local process without elevated rights, making it relatively easy for local attackers or compromised software. While the impact is limited to service disruption, the low external attack surface reduces immediate risks, yet patching remains advisable.