# CVE-2026-50248: NLnet Labs Unbound insufficient verification of XFR endpoints in RPZ zones

Source: https://junglewise.ai/threats/cve-2026-50248-nlnet-labs-unbound-insufficient-verification-of-xfr-endpoints-in  
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-2026-50248 · Severity: medium · CVSS 6.5 · Published 2026-07-22

Unbound is a widely used DNS resolver that helps translate human-readable website names into IP addresses. A security flaw allows an attacker to trick the system into accepting fake DNS records by spoofing the identity of a primary data source. This could allow an attacker to redirect network traffic or block access to legitimate websites by replacing the resolver's entire response policy.

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

## Quick answers

**Is CVE-2026-50248 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-50248 being exploited in the wild.

**How severe is CVE-2026-50248?** Medium severity, with a CVSS score of 6.5, published 22 July 2026.

**Which products and versions are affected?** NLnet Labs Unbound 1.7.0 to 1.25.1.

**Is there a fix for CVE-2026-50248?** A patch was published on 2026-07-22: Fixed in Unbound version 1.25.2 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-50248 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-50248?** 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 handling of authoritative (auth) and Response Policy Zones (RPZ) when a primary hostname resolves to a BOGUS DNSSEC state. Unbound incorrectly treats these BOGUS A/AAAA records as valid XFR endpoints. An attacker capable of spoofing these records (without needing a valid RRSIG) can position themselves as the primary XFR server. This allows the attacker to push a malicious zone transfer, effectively replacing the entire zone or response policy. The issue is fixed in version 1.25.2 by ensuring BOGUS hostnames are disregarded for XFR endpoints.

## Affected products

- NLnet Labs Unbound 1.7.0 to 1.25.1

## Timeline

- 2026-07-22: advisory: NLnet Labs released advisory and patch for CVE-2026-50248
- 2026-07-22: patched: Fixed in Unbound version 1.25.2

## References

- [https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-50248.txt](https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-50248.txt)

## Related threats

- [NLnet Labs Unbound use-after-free in DNS-over-QUIC stream cleanup](https://junglewise.ai/threats/cve-2026-97206-nlnet-labs-unbound-1-22-0-up-to-and-including-version-1-26-1)
- [NLnet Labs Unbound DNS decompression CPU exhaustion](https://junglewise.ai/threats/cve-2026-96405-nlnet-labs-unbound-up-to-and-including-version-1-26-1-limits)
- [NLnet Labs Unbound DNS validator bypass in DNSSEC validation](https://junglewise.ai/threats/cve-2026-50106-when-nlnet-labs-unbound-up-to-and-including-version-1-26-1-is)
- [NLnet Labs Unbound cache side-channel in upstream source port probe](https://junglewise.ai/threats/cve-2026-109125-in-nlnet-labs-unbound-up-to-and-including-version-1-26-1-an)
- [NLnet Labs Unbound DNS complexity attacks via ReTrap](https://junglewise.ai/threats/cve-2026-85501-nlnet-labs-unbound-dns-complexity-attacks-via-retrap)