CVE-2017-6519: avahi-daemon in Avahi through 0.6.32 and 0.7 inadvertently responds to IPv6 unicast queries with source addres

Q: How do I fix CVE-2017-6519?

avahi: upgrade to newer than 0.6.32; ubuntu linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2017-6519 being exploited?

CVE-2017-6519 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2017-6519 affect?

CVE-2017-6519 affects avahi, ubuntu linux. Severity is critical (CVSS 9.1). 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 informa

Q: How urgent is CVE-2017-6519?

Priority 69/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

This week

CRITICAL 9.1REMOTEWATCHLISTUPGRADEMITIGATE

CVE-2017-6519 is a critical-severity flaw (CVSS 9.1) affecting avahi, ubuntu linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	3.2% (top 12%)
CISA exploited list	No
Weakness	CWE-346
Published	2017-05-01
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: avahi · canonical

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2017-05-01 01:59 UTCPublished CVE record published
2026-06-17 01:22 UTCUpdated Record last modified

avahi avahi UPGRADE

Affected: <= 0.6.32 · 0.7

Fixed in: newer than 0.6.32

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy avahi || rpm -q avahi || avahi --version

2. UPGRADE to newer than 0.6.32 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade avahi

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade avahi

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

canonical ubuntu linux MITIGATE

Affected: 12.04 · 14.04 · 16.04 · 18.04 · 18.10

Fixed in: no fixed release known

Safe to downgrade to: a release before 12.04

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora ELN · fuse-sshfs · FIXED · 3.7.6-3.eln159 · FEDORA-2026-bcb7be7c5c · source

sudo dnf upgrade --advisory=FEDORA-2026-bcb7be7c5c

Fedora 46 · python-odata-query · FIXED · 0.10.1-1.fc46 · FEDORA-2026-eab44dc513 · source

sudo dnf upgrade --advisory=FEDORA-2026-eab44dc513

Debian 12 · avahi · FIXED · 0.7-5

sudo apt update && sudo apt install --only-upgrade avahi dpkg --compare-versions "$(dpkg-query -W -f='${Version}' avahi)" ge "0.7-5" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · avahi · FIXED · 0.7-5

sudo apt update && sudo apt install --only-upgrade avahi dpkg --compare-versions "$(dpkg-query -W -f='${Version}' avahi)" ge "0.7-5" && echo PATCHED || echo STILL-VULNERABLE

RHEL 7 · avahi · FIXED · avahi-0.6.31-20.el7

sudo dnf upgrade --advisory=RHSA-2020:1176 rpm -q avahi

RHEL 5 · avahi · DEFERRED

RHEL 6 · avahi · DEFERRED

RHEL 8 · avahi · DEFERRED

RHEL 9 · avahi · NO FIX YET

Alpine 3.20 · avahi · FIXED · avahi-0.7-r2

apk add --upgrade avahi apk info -v avahi

Alpine 3.21 · avahi · FIXED · avahi-0.7-r2

apk add --upgrade avahi apk info -v avahi

Alpine 3.22 · avahi · FIXED · avahi-0.7-r2

apk add --upgrade avahi apk info -v avahi

Alpine 3.23 · avahi · FIXED · avahi-0.7-r2

apk add --upgrade avahi apk info -v avahi

Amazon Linux 2 · see advisory · FIXED · ALAS2-2020-1502 · source

sudo yum update --advisory=ALAS2-2020-1502

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: usn.ubuntu.com/3876-2/

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2017-6519?

avahi: upgrade to newer than 0.6.32; ubuntu linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2017-6519 being exploited?

CVE-2017-6519 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2017-6519 affect?

CVE-2017-6519 affects avahi, ubuntu linux. Severity is critical (CVSS 9.1). 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 informa

How urgent is CVE-2017-6519?

Priority 69/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Ubuntu vulnerabilities

Related CVEs

CVE-2023-38473 MEDIUM 6.2 UPGRADE MITIGATE A vulnerability was found in Avahi
CVE-2023-38472 MEDIUM 6.2 UPGRADE MITIGATE A vulnerability was found in Avahi
CVE-2023-38471 MEDIUM 6.2 UPGRADE MITIGATE A vulnerability was found in Avahi
CVE-2023-38470 MEDIUM 6.2 UPGRADE MITIGATE A vulnerability was found in Avahi
CVE-2023-38469 MEDIUM 6.2 UPGRADE MITIGATE A vulnerability was found in Avahi, where a reachable assertion exists in avahi_dns_packet_append_record.

References

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