CVE-2021-26720

What it is

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.

At a glance

Exploitability

Can be exploited locally on the machine with a low-privilege account. High risk of data exposure, data tampering, service disruption.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

1. 2021-02-05 00:00 UTC ReservedThe CVE id was reserved by its CNA
2. 2021-02-17 22:15 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-06-17 03:43 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.4% in the next 30 days (EPSS).
• Severity: 7.8 HIGH (CVSS).
• Fix: none linked yet, which raises it.

Details

Published

2021-02-17 22:15 UTC

Last modified

2026-06-17 03:43 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-59

Record status

Modified

Affected

• Avahi ≤ 0.8-4
• Debian Linux 9.0
• Debian Linux 10.0

Attack profile CVSS 3.1 · 7.8

Attack vector

Local

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-26720.md and follow it. Check whether this project is affected by CVE-2021-26720. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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