{"id":"CVE-2025-59529","summary":"simple protocol server ignores accepts unlimited connections and logs failures without limit","details":"Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. In versions up to and including 0.9-rc2, the simple protocol server ignores the documented client limit and accepts unlimited connections, allowing for easy local DoS. Although `CLIENTS_MAX` is defined, `server_work()` unconditionally `accept()`s and `client_new()` always appends the new client and increments `n_clients`. There is no check against the limit. When client cannot be accepted as a result of maximal socket number of avahi-daemon, it logs unconditionally error per each connection. Unprivileged local users can exhaust daemon memory and file descriptors, causing a denial of service system-wide for mDNS/DNS-SD. Exhausting local file descriptors causes increased system load caused by logging errors of each of request. Overloading prevents glibc calls using nss-mdns plugins to resolve `*.local.` names and link-local addresses. As of time of publication, no known patched versions are available, but a candidate fix is available in pull request 808, and some workarounds are available. Simple clients are offered for nss-mdns package functionality. It is not possible to disable the unix socket `/run/avahi-daemon/socket`, but resolution requests received via DBus are not affected directly. Tools avahi-resolve, avahi-resolve-address and avahi-resolve-host-name are not affected, they use DBus interface. It is possible to change permissions of unix socket after avahi-daemon is started. But avahi-daemon does not provide any configuration for it. Additional access restrictions like SELinux can also prevent unwanted tools to access the socket and keep resolution working for trusted users.","aliases":["GHSA-73wf-3xmj-x82q"],"modified":"2026-04-10T05:34:10.171253Z","published":"2025-12-18T20:25:31.499Z","related":["CGA-443m-9wpv-xvh7"],"database_specific":{"cwe_ids":["CWE-400"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/59xxx/CVE-2025-59529.json","cna_assigner":"GitHub_M"},"references":[{"type":"WEB","url":"http://www.openwall.com/lists/oss-security/2025/12/19/1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/59xxx/CVE-2025-59529.json"},{"type":"ADVISORY","url":"https://github.com/avahi/avahi/security/advisories/GHSA-73wf-3xmj-x82q"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-59529"},{"type":"FIX","url":"https://github.com/avahi/avahi/pull/808"},{"type":"ARTICLE","url":"https://zeropath.com/blog/avahi-simple-protocol-server-dos-cve-2025-59529"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/avahi/avahi","events":[{"introduced":"0"},{"last_affected":"1dade81cbf4d3e3f49784e44e543cd77046c79df"}],"database_specific":{"versions":[{"introduced":"0"},{"last_affected":"0.9-rc2"}]}}],"versions":["0.6.32-rc","v0.6.23","v0.6.24","v0.6.25","v0.6.26","v0.6.27","v0.6.28","v0.6.29","v0.6.30","v0.6.31","v0.6.32","v0.7","v0.8","v0.9-rc1","v0.9-rc2"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-59529.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/lathiat/avahi","events":[{"introduced":"0"},{"last_affected":"8ee3bd6f7921b489bde14f120187a5becf134d30"}],"database_specific":{"versions":[{"introduced":"0"},{"last_affected":"0.9-rc1"}]}}],"versions":["0.6.32-rc","v0.6.23","v0.6.24","v0.6.25","v0.6.26","v0.6.27","v0.6.28","v0.6.29","v0.6.30","v0.6.31","v0.6.32","v0.7","v0.8","v0.9-rc1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-59529.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}