CVE-2026-44690 Details
Description
In NLnet Labs Unbound 1.7.0 up to and including 1.25.1, insufficient validation of the RRSIG.Labels field combined with premature cache writes during RFC 8198 aggressive NSEC processing leads to cache poisoning that permits a malicious actor controlling a single delegated zone to poison arbitrary sibling zones under NSEC-signed parent domains. A malicious actor with one registered domain under an NSEC-signed TLD can serve malicious insecure DNS responses for unrelated sibling domains (sharing the same parent zone). Arbitrary delegations that do not exist under the parent domain and are covered by the parent's NSEC chain can be brought into insecure existence by fraudulent wildcard DS records (less labels than expected, unknown algorithm) from the malicious sibling domain. This allows the malicious actor to inject insecure wildcard records for those delegations.
A cache poisoning vulnerability has been identified in NLnet Labs Unbound versions 1.7.0 prior to 1.25.1. The issue arises from inadequate validation of the RRSIG.Labels field and premature cache writes during aggressive NSEC processing, as per RFC 8198. This vulnerability allows a malicious actor with a registered domain under an NSEC-signed top-level domain (TLD) to inject insecure DNS responses for unrelated sibling domains within the same parent zone. Additionally, the vulnerability enables the exploitation of arbitrary delegations covered by the parent's NSEC chain, using fraudulent wildcard DS records from the malicious sibling domain to create insecure wildcard records for those delegations.
Users can upgrade to Unbound version 1.25.2, which includes the necessary fixes. For those using Unbound 1.25.1, a manual patch is available and can be applied by following the provided instructions.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jul 22, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-44690.txt | [email protected] | Vendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-345 | Insufficient Verification of Data Authenticity | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| nlnetlabs unbound | >= 1.7.0, < 1.25.2 |
CPE
Remediation
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Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 24, 2026 | Initial Analysis | [email protected] |
| Jul 22, 2026 | CVE Modified | CISA-ADP |
| Jul 22, 2026 | New CVE Received | [email protected] |