What is CVE-2026-55973?

CVE-2026-55973 is a high-severity vulnerability in Nlnet Labs Unbound, classified under Improper Input Validation. CVSS score: 7.5/10. Published 2026-07-22.

How severe is CVE-2026-55973?

High severity. CVSS v3 base score is 7.5 out of 10.

Improper input validation in Nlnet Labs Unbound

CVE-2026-55973

In NLnet Labs Unbound 1.23.0 up to and including 1.25.1, when 'dns-error-reporting: yes' is set, the EDNS Report-Channel option (code 18) from the last upstream response is read and uses the option's length as the length of the agent domai…

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Nlnet Labs Unbound — versions 1.23.0

Weakness classification (CWE)

CWE-20 — Improper Input Validation

References

sep@nlnetlabs.nl (vendor-advisory)

Frequently asked questions

What is CVE-2026-55973?: CVE-2026-55973 is a high-severity vulnerability in Nlnet Labs Unbound, classified under Improper Input Validation. CVSS score: 7.5/10. Published 2026-07-22.
How severe is CVE-2026-55973?: High severity. CVSS v3 base score is 7.5 out of 10.