# CVE-2021-3468: Denial of service in avahi > A local attacker can trigger an infinite loop in Avahi by mishandling client connection termination, causing the service to become unresponsive. - **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:** 2 Jun 2021 - **Updated:** 13 Feb 2025 - **Also known as:** ALPINE-CVE-2021-3468, AZL-34548, AZL-6324, DEBIAN-CVE-2021-3468, DLA-3466-1, GHSA-43rm-fv4g-cmj8, MGASA-2021-0212, OESA-2021-1232, SUSE-SU-2021:1493-1, SUSE-SU-2021:1493-2, SUSE-SU-2021:1494-1, SUSE-SU-2021:1494-2, UBUNTU-CVE-2021-3468, USN-5008-2, openSUSE-SU-2021:0694-1 ## What is CVE-2021-3468? CVE-2021-3468 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 2 Jun 2021. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description A flaw was found in avahi in versions 0.6 up to 0.8. The event used to signal the termination of the client connection on the avahi Unix socket is not correctly handled in the client_work function, allowing a local attacker to trigger an infinite loop. The highest threat from this vulnerability is to the availability of the avahi service, which becomes unresponsive after this flaw is triggered. Weakness: CWE-835 (Loop with Unreachable Exit Condition) ## Which versions are affected by CVE-2021-3468? It affects 2 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `avahi` | SUSE:Enterprise Storage 6 | All versions | 0.7-3.9.1 | | `avahi-glib2` | SUSE:Enterprise Storage 6 | All versions | 0.7-3.9.1 | | `avahi` | SUSE:HPE Helion OpenStack 8 | All versions | 0.6.32-32.15.1 | | `avahi-glib2` | SUSE:HPE Helion OpenStack 8 | All versions | 0.6.32-32.15.1 | | `avahi` | SUSE:Linux Enterprise High Performance Computing 15 SP1-ESPOS | All versions | 0.7-3.9.1 | | `avahi-glib2` | SUSE:Linux Enterprise High Performance Computing 15 SP1-ESPOS | All versions | 0.7-3.9.1 | | `avahi` | SUSE:Linux Enterprise High Performance Computing 15 SP1-LTSS | All versions | 0.7-3.9.1 | | `avahi-glib2` | SUSE:Linux Enterprise High Performance Computing 15 SP1-LTSS | All versions | 0.7-3.9.1 | | `avahi` | SUSE:Linux Enterprise Module for Basesystem 15 SP2 | All versions | 0.7-3.9.1 | | `avahi-glib2` | SUSE:Linux Enterprise Module for Basesystem 15 SP2 | All versions | 0.7-3.9.1 | | `avahi` | SUSE:Linux Enterprise Module for Basesystem 15 SP3 | All versions | 0.7-3.9.1 | | `avahi-glib2` | SUSE:Linux Enterprise Module for Basesystem 15 SP3 | All versions | 0.7-3.9.1 | | `avahi` | SUSE:Linux Enterprise Module for Desktop Applications 15 SP2 | All versions | 0.7-3.9.1 | | `avahi-glib2` | SUSE:Linux Enterprise Module for Desktop Applications 15 SP2 | All versions | 0.7-3.9.1 | | `avahi` | SUSE:Linux Enterprise Module for Desktop Applications 15 SP3 | All versions | 0.7-3.9.1 | | `avahi-glib2` | SUSE:Linux Enterprise Module for Desktop Applications 15 SP3 | All versions | 0.7-3.9.1 | | `avahi` | SUSE:Linux Enterprise Module for Package Hub 15 SP2 | All versions | 0.7-3.9.1 | | `avahi` | SUSE:Linux Enterprise Module for Package Hub 15 SP3 | All versions | 0.7-3.9.1 | | `avahi` | SUSE:Linux Enterprise Server 12 SP2-BCL | All versions | 0.6.32-32.15.1 | | `avahi-glib2` | SUSE:Linux Enterprise Server 12 SP2-BCL | All versions | 0.6.32-32.15.1 | | `avahi` | SUSE:Linux Enterprise Server 12 SP3-BCL | All versions | 0.6.32-32.15.1 | | `avahi-glib2` | SUSE:Linux Enterprise Server 12 SP3-BCL | All versions | 0.6.32-32.15.1 | | `avahi` | SUSE:Linux Enterprise Server 12 SP3-LTSS | All versions | 0.6.32-32.15.1 | | `avahi-glib2` | SUSE:Linux Enterprise Server 12 SP3-LTSS | All versions | 0.6.32-32.15.1 | | `avahi` | SUSE:Linux Enterprise Server 12 SP4-LTSS | All versions | 0.6.32-32.15.1 | | `avahi-glib2` | SUSE:Linux Enterprise Server 12 SP4-LTSS | All versions | 0.6.32-32.15.1 | | `avahi` | SUSE:Linux Enterprise Server 12 SP5 | All versions | 0.6.32-32.15.1 | | `avahi-glib2` | SUSE:Linux Enterprise Server 12 SP5 | All versions | 0.6.32-32.15.1 | | `avahi` | SUSE:Linux Enterprise Server 15 SP1-BCL | All versions | 0.7-3.9.1 | | `avahi-glib2` | SUSE:Linux Enterprise Server 15 SP1-BCL | All versions | 0.7-3.9.1 | | `avahi` | SUSE:Linux Enterprise Server 15 SP1-LTSS | All versions | 0.7-3.9.1 | | `avahi-glib2` | SUSE:Linux Enterprise Server 15 SP1-LTSS | All versions | 0.7-3.9.1 | | `avahi` | SUSE:Linux Enterprise Server for SAP Applications 12 SP3 | All versions | 0.6.32-32.15.1 | | `avahi-glib2` | SUSE:Linux Enterprise Server for SAP Applications 12 SP3 | All versions | 0.6.32-32.15.1 | | `avahi` | SUSE:Linux Enterprise Server for SAP Applications 12 SP4 | All versions | 0.6.32-32.15.1 | | `avahi-glib2` | SUSE:Linux Enterprise Server for SAP Applications 12 SP4 | All versions | 0.6.32-32.15.1 | | `avahi` | SUSE:Linux Enterprise Server for SAP Applications 12 SP5 | All versions | 0.6.32-32.15.1 | | `avahi-glib2` | SUSE:Linux Enterprise Server for SAP Applications 12 SP5 | All versions | 0.6.32-32.15.1 | | `avahi` | SUSE:Linux Enterprise Server for SAP Applications 15 SP1 | All versions | 0.7-3.9.1 | | `avahi-glib2` | SUSE:Linux Enterprise Server for SAP Applications 15 SP1 | All versions | 0.7-3.9.1 | Products: Avahi Avahi, Debian Debian Linux. ## How do I fix CVE-2021-3468? Apply the vendor's patch. ## Is CVE-2021-3468 being exploited? There is no known exploitation of CVE-2021-3468 in the wild and no public exploit code. ## Other vulnerabilities in Debian Debian Linux - [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-2021-3468 and fix it if it is affected. What it is: CVE-2021-3468 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 2 Jun 2021. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2021-3468 in the wild and no public exploit code. Affected product: Debian Debian Linux. 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-2021-3468/ (Markdown: https://insights.sbomify.com/CVE-2021-3468/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3468 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3468 - OSV: https://osv.dev/vulnerability/CVE-2021-3468 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-3468/ Summaries are generated and may contain mistakes; the official description above is the record.