Medium severity · published Jul 22, 2026
CVE-2026-50248
BOGUS configured primary hostname accepted for XFR in auth/rpz zones
6.5
CVSS
0.1%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
None
Integrity
High
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.1% · higher than 3% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
UN
Unbound · NLnet Labs
1.7.0 before 1.25.2 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-50248
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-50248
Vendor Advisory
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-50248.txt
More from Unbound
10.0
CVE-2026-42960
Possible cache poisoning via promiscuous records for the authority section
9.8
CVE-2026-82717
CNAME synthesis could lead to heap corruption
9.8
CVE-2026-81642
Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY
9.8
CVE-2026-33278
Possible arbitrary code execution during DNSSEC validation
9.3
CVE-2026-50252
Possible cache poisoning attack by mapping source port population per thread