CVE-2026-55708: NLnet Labs Unbound insecure default initialization in unbound-control

CVE-2026-55708 · Severity: low · CVSS 3.1 · Published 2026-07-22

A vulnerability in the Unbound DNS resolver could allow sensitive internal network information to be leaked to the public internet. When administrators use specific management commands to update configuration, the system may fail to apply standard security protections for private addresses. This results in internal queries for private resources being sent to public servers, potentially exposing internal network structure or bypassing local security policies.

Technologies: NLnet Labs Unbound. Vendors: NLnet Labs.

Quick answers

Is CVE-2026-55708 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55708 being exploited in the wild.
How severe is CVE-2026-55708?
Low severity, with a CVSS score of 3.1, published 22 July 2026.
Which products and versions are affected?
NLnet Labs Unbound 1.6.0 to 1.25.1.
Is there a fix for CVE-2026-55708?
A patch was published on 2026-07-22: Fixed in version 1.25.2 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-55708 attacked?
It is attacked with local access, in a hosted service.
Am I affected by CVE-2026-55708?
Check whether you run NLnet Labs Unbound at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

In NLnet Labs Unbound versions 1.6.0 through 1.25.1, the 'view_local_data' and 'view_local_datas' commands in 'unbound-control' fail to initialize default-protected zones (such as RFC 1918, AS112, .onion, and .localhost) when creating a new local zone tree for an existing view. This insecure default initialization (CWE-1188) occurs when a view is initially configured without local data. Consequently, queries for these protected names are forwarded to public DNS iterators instead of being handled locally. An attacker with high-privilege access to the control interface could trigger this state, leading to information leakage and policy bypass. The issue is resolved in version 1.25.2.

Affected products

  • NLnet Labs Unbound 1.6.0 to 1.25.1

Timeline

  • 2026-07-22: disclosed
  • 2026-07-22: advisory
  • 2026-07-22: patched: Fixed in version 1.25.2

References

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