CVE-2026-50248: nlnet labs unbound
Vulnerability summary
CVE-2026-50248 is a medium (CVSS 6.5) vulnerability in nlnet labs unbound. EPSS estimates a 0.13% chance of exploitation in the next 30 days, higher than 2.1% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 15 · Related 12Timeline
- 22-07-2026PublishedVulnerability first disclosed.
- 22-07-2026Last modifiedVulnerability information updated.
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 metrics
5 scores · 5 sources · 1 version- OSV · AlpineEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L
- OSV · UbuntuEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L
- OSV · DebianEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L
- NVDNIST6.5MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L
EPSS trend
Probability
0.13%
Chance of exploitation in the next 30 days
Percentile
2%
Versus all other CVEs
30-day change
0.00 pp
From 0.13% on 19-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Alpine1 product
- unbound≥ 1.7.0, < 1.25.2-r0
Debian1 product
- unboundAll versions (No fix recorded) | < 1.26.1-0+deb13u1 | < 1.25.2-1
Nlnet labs1 product
- unbound≥ 1.7.0, < 1.25.2
Nlnetlabs1 product
- unbound≥ 1.7.0, < 1.25.2
Ubuntu1 product
- unboundAll versions (No fix recorded)
5 vendors · 5 products
References
7 links- www.nlnetlabs.nl/downloads/unbound/CVE-2026-50248.txtVendor Advisory
