CVE-2026-44687 - Low Severity Vulnerability
Vulnerable Library - src4.0.4
Library home page: https://github.com/MidnightBSD/src.git
Found in base branches: stable/4.0, master
Vulnerable Source Files (1)
Vulnerability Details
In NLnet Labs Unbound 1.13.2 up to and including 1.25.1, stub or forward zones where the name is below an intermediate labed below a DNSSEC signed zone could be shadowed by the intermediate label's secure NXDOMAIN answer from the parent. This is caused by an off-by-one error in 'harden-below-nxdomain' logic; enabled by default. It effectively bypasses the configuration and the configured stub/forward zone is never contacted. 'harden-below-nxdomain' does an upward DNS cache walk together with a delegation point guard that does not allow NXDOMAIN synthesis above stub/forward zones. The guard tests the domain name but before stripping a label. This results in an iteration where the domain name equals the configured stub/forward zone apex that passes the guard, strips one more label, and probes the cache at the apex's immediate public parent. If that parent has a cached DNSSEC-secure NXDOMAIN, which it will for any private namespace nested two or more labels under a signed public name, the walk returns it and the configured stub/forward upstream is never contacted. This can only be triggered by the query for the intermediate label (between the stub/forward apex and the DNSSEC parent zone).
Publish Date: 2026-07-22
URL: CVE-2026-44687
CVSS 3 Score Details (3.7)
Base Score Metrics:
- Exploitability Metrics:
- Attack Vector: Network
- Attack Complexity: High
- Privileges Required: None
- User Interaction: None
- Scope: Unchanged
- Impact Metrics:
- Confidentiality Impact: None
- Integrity Impact: None
- Availability Impact: Low
For more information on CVSS3 Scores, click here.
Suggested Fix
Type: Upgrade version
Release Date: 2026-07-22
Fix Resolution: https://github.com/NLnetLabs/unbound.git - release-1.25.2
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CVE-2026-44687 - Low Severity Vulnerability
Library home page: https://github.com/MidnightBSD/src.git
Found in base branches: stable/4.0, master
In NLnet Labs Unbound 1.13.2 up to and including 1.25.1, stub or forward zones where the name is below an intermediate labed below a DNSSEC signed zone could be shadowed by the intermediate label's secure NXDOMAIN answer from the parent. This is caused by an off-by-one error in 'harden-below-nxdomain' logic; enabled by default. It effectively bypasses the configuration and the configured stub/forward zone is never contacted. 'harden-below-nxdomain' does an upward DNS cache walk together with a delegation point guard that does not allow NXDOMAIN synthesis above stub/forward zones. The guard tests the domain name but before stripping a label. This results in an iteration where the domain name equals the configured stub/forward zone apex that passes the guard, strips one more label, and probes the cache at the apex's immediate public parent. If that parent has a cached DNSSEC-secure NXDOMAIN, which it will for any private namespace nested two or more labels under a signed public name, the walk returns it and the configured stub/forward upstream is never contacted. This can only be triggered by the query for the intermediate label (between the stub/forward apex and the DNSSEC parent zone).
Publish Date: 2026-07-22
URL: CVE-2026-44687
Base Score Metrics:
- Exploitability Metrics:
- Attack Vector: Network
- Attack Complexity: High
- Privileges Required: None
- User Interaction: None
- Scope: Unchanged
- Impact Metrics:
- Confidentiality Impact: None
- Integrity Impact: None
- Availability Impact: Low
For more information on CVSS3 Scores, click here.Type: Upgrade version
Release Date: 2026-07-22
Fix Resolution: https://github.com/NLnetLabs/unbound.git - release-1.25.2
Step up your Open Source Security Game with Mend here