# CVE-2025-59529: Avahi: simple protocol server ignores accepts unlimited connections and logs failures without limit > Local attackers can exhaust system resources by opening unlimited connections to the Avahi daemon, causing a denial of service for mDNS resolution. - **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 18 Dec 2025 - **Updated:** 23 Oct 2026 - **Also known as:** AZL-72851, AZL-72853, BELL-CVE-2025-59529, CLSA-2026-1786360814, DEBIAN-CVE-2025-59529, ECHO-7e9e-9ac7-d59b, GHSA-73wf-3xmj-x82q, MINI-966h-8gfh-v72j, RHSA-2026:7411, ROOT-OS-DEBIAN-13-CVE-2025-59529, SUSE-SU-2026:22853-1, SUSE-SU-2026:22932-1, SUSE-SU-2026:23039-1, SUSE-SU-2026:23161-1, SUSE-SU-2026:3216-1, SUSE-SU-2026:3217-1, SUSE-SU-2026:3218-1, UBUNTU-CVE-2025-59529, openSUSE-SU-2026:11313-1, openSUSE-SU-2026:21417-1 ## What is CVE-2025-59529? CVE-2025-59529 is a medium-severity denial of service vulnerability in avahi, published on 18 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description 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-rc5, 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. Weakness: CWE-400 (Uncontrolled Resource Consumption) ## Which versions are affected by CVE-2025-59529? It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `avahi` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-autoipd` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-compat-howl` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-compat-howl-devel` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-compat-libdns_sd` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-compat-libdns_sd-devel` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-devel` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-dnsconfd` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-glib` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-glib-devel` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-gobject` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-gobject-devel` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-libs` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-qt3` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-qt3-devel` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-qt4` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-qt4-devel` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-qt5` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-qt5-devel` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-sharp` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-tools` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-ui` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-ui-devel` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-ui-gtk3` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-ui-sharp` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-ui-sharp-devel` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi-ui-tools` | Red Hat:hummingbird:1 | All versions | 0:0.9~rc2-8.1.hum1 | | `avahi` | SUSE:Linux Enterprise Micro 5.3 | All versions | 0.8-150400.7.34.1 | | `avahi` | SUSE:Linux Enterprise Micro 5.4 | All versions | 0.8-150400.7.34.1 | | `avahi` | SUSE:Linux Enterprise Micro 5.5 | All versions | 0.8-150400.7.34.1 | | `avahi` | SUSE:Linux Enterprise Module for Basesystem 15 SP7 | All versions | 0.8-150600.15.21.1 | | `avahi-glib2` | SUSE:Linux Enterprise Module for Basesystem 15 SP7 | All versions | 0.8-150600.15.21.1 | | `avahi` | SUSE:Linux Enterprise Module for Desktop Applications 15 SP7 | All versions | 0.8-150600.15.21.1 | | `avahi-glib2` | SUSE:Linux Enterprise Module for Desktop Applications 15 SP7 | All versions | 0.8-150600.15.21.1 | | `avahi` | SUSE:Linux Enterprise Module for Package Hub 15 SP7 | All versions | 0.8-150600.15.21.1 | | `avahi` | SUSE:Linux Enterprise Server 16.0 | All versions | 0.8-160000.6.1 | | `avahi-glib2` | SUSE:Linux Enterprise Server 16.0 | All versions | 0.8-160000.6.1 | | `avahi` | SUSE:Linux Enterprise Server LTSS Extended Security 12 SP5 | All versions | 0.6.32-32.45.1 | | `avahi` | SUSE:Linux Enterprise Server for SAP applications 16.0 | All versions | 0.8-160000.6.1 | | `avahi-glib2` | SUSE:Linux Enterprise Server for SAP applications 16.0 | All versions | 0.8-160000.6.1 | Products: Avahi Avahi. ## How do I fix CVE-2025-59529? No fix published yet. ## Is CVE-2025-59529 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-59529 exists. ## Other vulnerabilities in avahi - [CVE-2017-6519](https://insights.sbomify.com/CVE-2017-6519/): Denial of service in n/a (critical 9.1) - [CVE-2021-26720](https://insights.sbomify.com/CVE-2021-26720/): Path traversal in n/a (high 7.8) - [CVE-2026-24401](https://insights.sbomify.com/CVE-2026-24401/): Avahi has Uncontrolled Recursion in lookup_handle_cname function (medium 6.5) - [CVE-2025-68468](https://insights.sbomify.com/CVE-2025-68468/): Avahi has a reachable assertion in lookup_multicast_callback (medium 6.5) - [CVE-2025-68471](https://insights.sbomify.com/CVE-2025-68471/): Avahi has a reachable assertion in lookup_start (medium 6.5) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2025-59529 and fix it if it is affected. What it is: CVE-2025-59529 is a medium-severity denial of service vulnerability in avahi, published on 18 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-59529 exists. Affected product: avahi. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2025-59529/ (Markdown: https://insights.sbomify.com/CVE-2025-59529/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2025-59529 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-59529 - OSV: https://osv.dev/vulnerability/CVE-2025-59529 --- From sbomify Insights: https://insights.sbomify.com/CVE-2025-59529/ Summaries are generated and may contain mistakes; the official description above is the record.