← Vulnerability feed

Vulnerability record · CVE-2021-26720 · published 17 February 2021

CVE-2021-26720: Avahi link following vulnerability

Avahi · Avahi

avahi-daemon-check-dns.sh in the Debian avahi package through 0.8-4 is executed as root via /etc/network/if-up.d/avahi-daemon, and allows a local attacker to cause a denial of service or create arbitrary empty files via a symlink attack on files under /run/avahi-daemon. NOTE: this only affects the packaging for Debian GNU/Linux (used indirectly by SUSE), not the upstream Avahi product.

7.8 CVSS 3.1 High EPSS 0.40% · top 68.9% CWE-59 · Link following
7.8CVSS 3.1 base score, v2 4.6
0.40%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
20References
17 Jun 2026Last modified by NVD

Description

avahi-daemon-check-dns.sh in the Debian avahi package through 0.8-4 is executed as root via /etc/network/if-up.d/avahi-daemon, and allows a local attacker to cause a denial of service or create arbitrary empty files via a symlink attack on files under /run/avahi-daemon. NOTE: this only affects the packaging for Debian GNU/Linux (used indirectly by SUSE), not the upstream Avahi product.

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982796 Mailing ListThird Party Advisory
https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/1870824 Issue TrackingThird Party Advisory
https://bugzilla.suse.com/show_bug.cgi?id=1180827 Issue TrackingThird Party Advisory
https://lists.debian.org/debian-lts-announce/2022/06/msg00009.html Mailing ListThird Party Advisory
https://metadata.ftp-master.debian.org/changelogs/main/a/avahi/avahi_0.8-4_changelog Broken LinkThird Party Advisory
https://packages.debian.org/bullseye/avahi-daemon ProductThird Party Advisory
https://packages.debian.org/buster/avahi-daemon ProductThird Party Advisory
https://packages.debian.org/sid/avahi-daemon ProductThird Party Advisory
https://security-tracker.debian.org/tracker/CVE-2021-26720 Third Party Advisory
https://www.openwall.com/lists/oss-security/2021/02/15/2 Mailing ListThird Party Advisory
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982796 Mailing ListThird Party Advisory
https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/1870824 Issue TrackingThird Party Advisory
https://bugzilla.suse.com/show_bug.cgi?id=1180827 Issue TrackingThird Party Advisory
https://lists.debian.org/debian-lts-announce/2022/06/msg00009.html Mailing ListThird Party Advisory
https://metadata.ftp-master.debian.org/changelogs/main/a/avahi/avahi_0.8-4_changelog Broken LinkThird Party Advisory
https://packages.debian.org/bullseye/avahi-daemon ProductThird Party Advisory
https://packages.debian.org/buster/avahi-daemon ProductThird Party Advisory
https://packages.debian.org/sid/avahi-daemon ProductThird Party Advisory
https://security-tracker.debian.org/tracker/CVE-2021-26720 Third Party Advisory
https://www.openwall.com/lists/oss-security/2021/02/15/2 Mailing ListThird Party Advisory

Track CVE-2021-26720 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

10.0CVE-2025-32433Erlang/OTP SSH server missing authentication allows remote code executionErlang/OTP SSH servers before OTP-27.3.3, OTP-26.2.5.11 and OTP-25.3.2.20 mishandle SSH protocol messages, letting an unauthenticated attacker execut…KEVEPSS 99%analysed10.0CVE-2025-24201Apple WebKit out-of-bounds write allows sandbox escapeCVE-2025-24201 is an out-of-bounds write in Apple's WebKit that was addressed with improved checks. Maliciously crafted web content may break out of …KEVEPSS 3.8%analysed10.0CVE-2021-44228Apache Log4j2 JNDI lookup remote code executionApache Log4j2 versions 2.0-beta9 through 2.15.0 (excluding 2.12.2, 2.12.3, and 2.3.1) do not protect against attacker-controlled LDAP and other JNDI …KEVEPSS 100%analysed9.8CVE-2026-24061GNU Inetutils telnetd argument injection allows remote auth bypasstelnetd in GNU Inetutils through 2.7 fails to sanitize the USER environment variable, so a value such as "-f root" is passed as an argument to login …KEVEPSS 99%analysed9.8CVE-2025-39682Linux kernel TLS zero-length record handling flaw on rx_listThe Linux kernel TLS receive path mishandles zero-length records that arrive from the rx_list, breaking the assumption that a record type change cann…KEVEPSS 2.9%analysed9.8CVE-2025-24813Apache Tomcat Default Servlet path equivalence enables RCE and file disclosureApache Tomcat mishandles path equivalence for names containing an internal dot, letting a remote unauthenticated attacker write files through the Def…KEVEPSS 100%analysed9.8CVE-2024-9680Mozilla Firefox and Thunderbird use-after-free in Animation timelinesA use-after-free flaw in Animation timelines allows an attacker to execute code in the content process of Firefox and Thunderbird. Mozilla reports ex…KEVEPSS 23%analysed9.8CVE-2023-46604Apache ActiveMQ OpenWire deserialization remote code executionThe Java OpenWire protocol marshaller in Apache ActiveMQ deserializes untrusted data, letting an attacker manipulate serialized class types so the br…KEVEPSS 100%analysed

Source: NIST National Vulnerability Database (record CVE-2021-26720), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.