# CVE-2026-50243: NLnet Labs Unbound DNSSEC validation bypass in respip module

Source: https://junglewise.ai/threats/cve-2026-50243-nlnet-labs-unbound-dnssec-validation-bypass-in-respip-module  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-22. Updated: 2026-07-22  
License: CC BY 4.0 with a link back

CVE-2026-50243 · Severity: info · CVSS 6.3 · Published 2026-07-22

NLnet Labs Unbound, a widely used DNS resolver, contains a flaw in how it handles specific security rules for redirecting web traffic. Under certain configurations, the software may fail to verify the authenticity of a security-protected DNS response, allowing it to be redirected to an operator-defined IP address even if the response is invalid or forged. This could allow a remote attacker to bypass DNSSEC security protections and potentially misdirect users to unintended network locations.

Technologies: [NLnet Labs Unbound](https://junglewise.ai/threats/technologies/unbound). Vendors: [NLnet Labs](https://junglewise.ai/threats/vendors/nlnet-labs).

## Quick answers

**Is CVE-2026-50243 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-50243 being exploited in the wild.

**How severe is CVE-2026-50243?** Informational severity, with a CVSS score of 6.3, published 22 July 2026.

**Which products and versions are affected?** NLnet Labs Unbound 1.6.2 up to and including 1.25.1.

**Is there a fix for CVE-2026-50243?** 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-2026-50243 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-50243?** 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

A vulnerability exists in Unbound's 'respip' module when positioned before the validator in the module stack. When configured with 'response-ip' redirect rules or RPZ-IP triggers, the rewriting handler fails to validate the security status of upstream A/AAAA records. If an attacker spoofs a BOGUS answer (e.g., one with an expired RRSIG) that matches a configured subnet rewrite, Unbound will rewrite the answer to the operator's target IP and downgrade the security status to INSECURE rather than rejecting it. This allows DNSSEC-protected records to be insecurely redirected. The issue is fixed in Unbound version 1.25.2.

## Affected products

- NLnet Labs Unbound 1.6.2 up to and including 1.25.1

## Timeline

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

## References

- [https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-50243.txt](https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-50243.txt)

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