Executive brief
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.
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