CVE-2026-50248 BOGUS configured primary hostname accepted for XFR in auth/rpz zones
Attackers can spoof DNS records to become the primary for auth/rpz zones, allowing them to replace zone data or response policies in Unbound.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-50248?
CVE-2026-50248 is a medium-severity vulnerability in Nlnetlabs Unbound, published on 22 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when an auth/rpz zone has a configured primary hostname that resolves to BOGUS A/AAAA, it is still considered as a possible XFR endpoint. A malicious actor that can spoof the hostname's A/AAAA record (no valid RRSIG required) becomes the zone's XFR primary and can replaces the entire zone/the resolver's entire response policy.
Weakness: CWE-345
Which versions are affected by CVE-2026-50248?
It affects 1 product.
Products include Nlnetlabs Unbound.
How do I fix CVE-2026-50248?
Upgrade to a fixed version.
Is CVE-2026-50248 being exploited?
There is no known exploitation of CVE-2026-50248 in the wild and no public exploit code.
Other vulnerabilities in Nlnetlabs Unbound
- CVE-2026-81642 Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY
- CVE-2026-33278 Possible arbitrary code execution during DNSSEC validation
- CVE-2026-42944 Heap overflow with multiple NSID, COOKIE, PADDING EDNS options
- CVE-2026-42959 Crash during DNSSEC validation of malicious content
- CVE-2026-82717 CNAME synthesis could lead to heap corruption
Sources
Also known as ALPINE-CVE-2026-50248, AZL-92928, DEBIAN-CVE-2026-50248, ECHO-120d-ba58-fa3d, GHSA-vmhf-793v-3vr8, UBUNTU-CVE-2026-50248.