CVE-2026-44687

Published: Lug 22, 2026 Last Modified: Lug 24, 2026
ExploitDB:
Other exploit source:
Google Dorks:
LOW 3,7
Source: [email protected]
Attack Vector: network
Attack Complexity: high
Privileges Required: none
User Interaction: none
Scope: unchanged
Confidentiality: none
Integrity: none
Availability: low

Description

AI Translation Available

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).

193

Off-by-one Error

Draft
Abstraction: Base Structure: Simple
Common Consequences
Security Scopes Affected:
Availability Integrity Confidentiality Access Control
Potential Impacts:
Dos: Crash, Exit, Or Restart Dos: Resource Consumption (Cpu) Dos: Resource Consumption (Memory) Dos: Instability Modify Memory Execute Unauthorized Code Or Commands Bypass Protection Mechanism
Applicable Platforms
Languages: C, Not Language-Specific
View CWE Details
Application

Unbound by Nlnetlabs

Product Information
Vendor Nlnetlabs
Product Unbound
Version Range Affected
From 1.13.2 (inclusive)
To 1.25.2 (exclusive)
cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*
Common Platform Enumeration - Standardized vulnerability identification
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-44687.t…
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-44687.txt