RCE in Nlnet Labs Unbound

CVE-2026-55708

In NLnet Labs Unbound 1.6.0 up to and including 1.25.1, the 'view_local_data' and 'view_local_datas' commands of 'unbound-control' create a bare local zones tree for an already configured named view when the view is configured with no local data to begin with. However, the creation through the control interface omits adding the default-protected zones (e.g., RFC 1918 reverse, AS112 zones, .onion, .localhost). Once the local zone tree exists without the defaults, every query for a default-protected name from a client mapped to that view escapes to the public DNS via the iterator instead of being answered locally, bypassing local policy expectations.

EPSS: 0.002 (4.5th percentile) — read the EPSS interpretation.

CVSS v3 metric

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

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-55708?
CVE-2026-55708 is a low-severity vulnerability in Nlnet Labs Unbound, classified under Initialization of a Resource with an Insecure Default. CVSS score: 3.1/10. Published 2026-07-22.
How severe is CVE-2026-55708?
Low severity. CVSS v3 base score is 3.1 out of 10.