# CVE-2017-6519: Denial of service in n/a > Remote attackers can cause denial of service via traffic amplification and potentially leak sensitive information from Avahi mDNS responders. - **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 1 May 2017 - **Updated:** 3 Dec 2025 - **Also known as:** ALPINE-CVE-2017-6519, AZL-6322, CVE-2018-1000845, DEBIAN-CVE-2017-6519, GHSA-6vpj-pr2c-5mm2, MGASA-2019-0081, RHSA-2020:1176, UBUNTU-CVE-2017-6519 ## What is CVE-2017-6519? CVE-2017-6519 is a critical denial of service vulnerability in Canonical Ubuntu Linux, published on 1 May 2017. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description avahi-daemon in Avahi through 0.6.32 and 0.7 inadvertently responds to IPv6 unicast queries with source addresses that are not on-link, which allows remote attackers to cause a denial of service (traffic amplification) and may cause information leakage by obtaining potentially sensitive information from the responding device via port-5353 UDP packets. NOTE: this may overlap CVE-2015-2809. Weakness: CWE-346 (Origin Validation Error) ## Which versions are affected by CVE-2017-6519? It affects 2 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `avahi` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-autoipd` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-compat-howl` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-compat-howl-devel` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-compat-libdns_sd` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-compat-libdns_sd-devel` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-debuginfo` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-devel` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-dnsconfd` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-glib` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-glib-devel` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-gobject` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-gobject-devel` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-libs` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-qt3` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-qt3-devel` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-qt4` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-qt4-devel` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-tools` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-ui` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-ui-devel` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-ui-gtk3` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi-ui-tools` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6.31-20.el7 | | `avahi` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | | `avahi-autoipd` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | | `avahi-compat-howl` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | | `avahi-compat-howl-devel` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | | `avahi-compat-libdns_sd` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | | `avahi-compat-libdns_sd-devel` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | | `avahi-debuginfo` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | | `avahi-devel` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | | `avahi-dnsconfd` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | | `avahi-glib` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | | `avahi-glib-devel` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | | `avahi-gobject` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | | `avahi-gobject-devel` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | | `avahi-libs` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | | `avahi-qt3` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | | `avahi-qt3-devel` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | | `avahi-qt4` | Red Hat:enterprise_linux:7::computenode | All versions | 0:0.6.31-20.el7 | Products: Avahi Avahi, Canonical Ubuntu Linux. ## How do I fix CVE-2017-6519? Apply the vendor's patch. ## Is CVE-2017-6519 being exploited? There is no known exploitation of CVE-2017-6519 in the wild and no public exploit code. ## Other vulnerabilities in Canonical Ubuntu Linux - [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) - [CVE-2023-38469](https://insights.sbomify.com/CVE-2023-38469/): Reachable assertion in avahi_dns_packet_append_record (medium 6.2) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2017-6519 and fix it if it is affected. What it is: CVE-2017-6519 is a critical denial of service vulnerability in Canonical Ubuntu Linux, published on 1 May 2017. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2017-6519 in the wild and no public exploit code. Affected product: Canonical Ubuntu 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-2017-6519/ (Markdown: https://insights.sbomify.com/CVE-2017-6519/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2017-6519 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-6519 - OSV: https://osv.dev/vulnerability/CVE-2017-6519 --- From sbomify Insights: https://insights.sbomify.com/CVE-2017-6519/ Summaries are generated and may contain mistakes; the official description above is the record.