CVE-2026-50248: In NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when an auth/rpz zone has a configured primary hostnam

Routine

MEDIUM 6.5REMOTEUPGRADE

CVE-2026-50248 is a medium-severity flaw (CVSS 6.5) affecting unbound. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.1% (top 97%)
CISA exploited list	No
Weakness	CWE-345
Published	2026-07-22
Last modified	2026-10-24

Publisher (CNA): NLnet Labs · Vendor: nlnetlabs

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-22 14:17 UTCPublished CVE record published
2026-10-24 13:10 UTCUpdated Record last modified

nlnetlabs unbound UPGRADE

Affected: >= 1.7.0 and < 1.25.2

Fixed in: 1.25.2

Safe to downgrade to: a release before 1.7.0

1. Check installed version

apt-cache policy unbound || rpm -q unbound || unbound --version

2. UPGRADE to 1.25.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade unbound

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade unbound

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 1.7.0 (Debian / Ubuntu)

apt-cache madison unbound sudo apt install unbound=<VERSION_BEFORE_1.7.0> sudo apt-mark hold unbound

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list unbound sudo dnf downgrade unbound-<VERSION_BEFORE_1.7.0> sudo dnf versionlock add unbound

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-50248?

unbound: upgrade to 1.25.2. Exact commands for each OS are on this page.

Is CVE-2026-50248 being exploited?

CVE-2026-50248 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-50248 affect?

CVE-2026-50248 affects unbound. Severity is medium (CVSS 6.5). 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'

How urgent is CVE-2026-50248?

Priority 28/100. Remotely exploitable, no login, no user action

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References

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