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Fencer Vulns
medium 5.5

CVE-2021-3468 json

A flaw was found in avahi in versions 0.6 up to 0.8.

published 2021-06-02 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-26790

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits
0
none known

Summary

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.

Patch / fix

  • avahi Debian 14, Debian 13, Debian 12 0.8-7

debian advisories DEBIAN-CVE-2021-3468

  • avahi Ubuntu 18.04 LTS 0.7-3.1ubuntu1.3
  • avahi Ubuntu 20.04 LTS 0.7-4ubuntu7.1
  • avahi Ubuntu Pro 14.04 LTS 0.6.31-4ubuntu1.3+esm1
  • avahi Ubuntu Pro 16.04 LTS 0.6.32~rc+dfsg-1ubuntu2.3+esm1

ubuntu advisories UBUNTU-CVE-2021-3468

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • avahi RHEL 8 0.7-21.el8_9.1
  • avahi-ui RHEL 8 0.7-21.el8_9.1
  • avahi-glib RHEL 8 0.7-21.el8_9.1
  • avahi-libs RHEL 8 0.7-21.el8_9.1
  • avahi-tools RHEL 8 0.7-21.el8_9.1
  • avahi-autoipd RHEL 8 0.7-21.el8_9.1
  • avahi-gobject RHEL 8 0.7-21.el8_9.1
  • avahi-ui-gtk3 RHEL 8 0.7-21.el8_9.1

red hat advisories RHSA-2024:0576RHSA-2024:0418RHSA-2023:7836RHSA-2023:6707

  • avahi SLES 15 SP1-BCL, SLE Module for Package Hub 15 SP3, SLE Module for Package Hub 15 SP2 +12 more 0.7-3.9.1
  • avahi-glib2 SLES 15 SP1-BCL, SLE Module for Desktop Applications 15 SP3, SLE Module for Desktop Applications 15 SP2 +10 more 0.7-3.9.1
  • avahi SLES 12 SP5, SLES 12 SP3-BCL, SLES 12 SP2-BCL +11 more 0.6.32-32.15.1
  • avahi-glib2 SLES 12 SP5, SLES 12 SP3-BCL, SLES 12 SP2-BCL +12 more 0.6.32-32.15.1
  • avahi SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 0.6.32-5.13.1
  • avahi-glib2 SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 0.6.32-5.13.1

suse advisories SUSE-SU-2021:1493-2SUSE-SU-2021:1494-2SUSE-SU-2021:1845-1SUSE-SU-2021:1494-1SUSE-SU-2021:1493-1

  • avahi openSUSE Tumbleweed 0.8-7.2
  • avahi openSUSE Leap 15.3 0.6.32-5.13.1
  • avahi-glib2 openSUSE Leap 15.3 0.6.32-5.13.1
  • avahi openSUSE Leap 15.2 0.7-lp152.3.9.1
  • avahi-qt4 openSUSE Leap 15.2 0.7-lp152.3.9.1
  • avahi-mono openSUSE Leap 15.2 0.7-lp152.3.9.1
  • avahi-glib2 openSUSE Leap 15.2 0.7-lp152.3.9.1

opensuse advisories openSUSE-SU-2024:10643-1openSUSE-SU-2021:1845-1openSUSE-SU-2021:0694-1

  • avahi AlmaLinux 8 0.7-21.el8_9.1
  • avahi-ui AlmaLinux 8 0.7-21.el8_9.1
  • avahi-glib AlmaLinux 8 0.7-21.el8_9.1
  • avahi-libs AlmaLinux 8 0.7-21.el8_9.1
  • avahi-tools AlmaLinux 8 0.7-21.el8_9.1
  • avahi-autoipd AlmaLinux 8 0.7-21.el8_9.1
  • avahi-gobject AlmaLinux 8 0.7-21.el8_9.1
  • avahi-ui-gtk3 AlmaLinux 8 0.7-21.el8_9.1

almalinux advisories ALSA-2023:7836ALSA-2023:6707

  • avahi Rocky Linux 8 0.7-21.el8_9.1

rocky linux advisories RLSA-2023:7836

  • avahi Alpine 3.12, Alpine 3.11 0.8-r1
  • avahi Alpine 3.13 0.8-r3
  • avahi Alpine 3.24, Alpine 3.23, Alpine 3.22 +8 more 0.8-r4

alpine advisories ALPINE-CVE-2021-3468

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • avahi CBL-Mariner 2.0, Azure Linux 3.0 0.8-1

azure linux advisories AZL-34548AZL-6324

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

  • avahi Arch Linux 1:0.8+r127+g55d783d-1

arch linux advisories AVG-1742

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-3468 updated cvss 6.2

avahi: Local DoS by event-busy-loop from writing long lines to /run/avahi-daemon/socket

  • Red Hat Enterprise Linux 6 avahi, avahi-ui, avahi-qt3, avahi-qt4, avahi-glib, avahi-libs, +7 more Red Hat Enterprise Linux 7 avahi, avahi-ui, avahi-qt3, avahi-qt4, avahi-glib, avahi-libs, +8 more
    affected: no fix planned “Out of support scope”
  • Red Hat CodeReady Linux Builder (v. 8) avahi-ui 0.7-21.el8_9.1, avahi-compat-howl 0.7-21.el8_9.1, avahi-compat-libdns_sd 0.7-21.el8_9.1
    fixed: vendor fix RHSA-2023:7836
  • Red Hat CodeReady Linux Builder (v. 9) avahi-compat-howl 0.8-15.el9, avahi-compat-libdns_sd 0.8-15.el9
    fixed: vendor fix RHSA-2023:6707
  • Red Hat CodeReady Linux Builder EUS (v.8.6) avahi-ui 0.7-20.el8_6.3, avahi-compat-howl 0.7-20.el8_6.3, avahi-compat-libdns_sd 0.7-20.el8_6.3
    fixed: vendor fix RHSA-2024:0418
  • Red Hat CodeReady Linux Builder EUS (v.8.8) avahi-ui 0.7-20.el8_8.4, avahi-compat-howl 0.7-20.el8_8.4, avahi-compat-libdns_sd 0.7-20.el8_8.4
    fixed: vendor fix RHSA-2024:0576
  • Red Hat Enterprise Linux AppStream (v. 8) avahi-tools 0.7-21.el8_9.1, avahi-ui-gtk3 0.7-21.el8_9.1
    fixed: vendor fix RHSA-2023:7836
  • Red Hat Enterprise Linux AppStream (v. 9) avahi-glib 0.8-15.el9, avahi-tools 0.8-15.el9
    fixed: vendor fix RHSA-2023:6707
  • Red Hat Enterprise Linux AppStream EUS (v.8.6) avahi-ui-gtk3 0.7-20.el8_6.3
    fixed: vendor fix RHSA-2024:0418
show 5 more
  • Red Hat Enterprise Linux AppStream EUS (v.8.8) avahi-ui-gtk3 0.7-20.el8_8.4
    fixed: vendor fix RHSA-2024:0576
  • Red Hat Enterprise Linux BaseOS (v. 8) avahi 0.7-21.el8_9.1, avahi-glib 0.7-21.el8_9.1, avahi-libs 0.7-21.el8_9.1, avahi-autoipd 0.7-21.el8_9.1, avahi-gobject 0.7-21.el8_9.1, python3-avahi 0.7-21.el8_9.1
    fixed: vendor fix RHSA-2023:7836
  • Red Hat Enterprise Linux BaseOS (v. 9) avahi 0.8-15.el9, avahi-libs 0.8-15.el9
    fixed: vendor fix RHSA-2023:6707
  • Red Hat Enterprise Linux BaseOS EUS (v.8.6) avahi 0.7-20.el8_6.3, avahi-glib 0.7-20.el8_6.3, avahi-libs 0.7-20.el8_6.3, avahi-autoipd 0.7-20.el8_6.3, avahi-gobject 0.7-20.el8_6.3, python3-avahi 0.7-20.el8_6.3
    fixed: vendor fix RHSA-2024:0418
  • Red Hat Enterprise Linux BaseOS EUS (v.8.8) avahi 0.7-20.el8_8.4, avahi-glib 0.7-20.el8_8.4, avahi-libs 0.7-20.el8_8.4, avahi-autoipd 0.7-20.el8_8.4, avahi-gobject 0.7-20.el8_8.4, python3-avahi 0.7-20.el8_8.4
    fixed: vendor fix RHSA-2024:0576

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 2.1 AV:L/AC:L/Au:N/C:N/I:N/A:P

Affected products

  • n/a avahi

Classification

Weakness
  • CWE-835 Loop with Unreachable Exit Condition

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.