What is CVE-2026-55717?

CVE-2026-55717 is a medium-severity vulnerability in Nlnet Labs Unbound, classified under NULL Pointer Dereference. CVSS score: 5.9/10. Published 2026-07-22.

How severe is CVE-2026-55717?

Medium severity. CVSS v3 base score is 5.9 out of 10.

NULL pointer dereference in Nlnet Labs Unbound

CVE-2026-55717

In NLnet Labs Unbound 1.10.0 up to and including 1.25.1, when 'serve-expired: yes' is set together with a 'response-ip: <net> redirect' /'response-ip-data: <net> CNAME <target>' rule (or the RPZ 'rpz-cname-override' equivalent), a remote c…

CVSS v3 metric

CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Nlnet Labs Unbound — versions 1.10.0

Weakness classification (CWE)

CWE-476 — NULL Pointer Dereference

References

sep@nlnetlabs.nl (vendor-advisory)

Frequently asked questions

What is CVE-2026-55717?: CVE-2026-55717 is a medium-severity vulnerability in Nlnet Labs Unbound, classified under NULL Pointer Dereference. CVSS score: 5.9/10. Published 2026-07-22.
How severe is CVE-2026-55717?: Medium severity. CVSS v3 base score is 5.9 out of 10.