CVE-2026-12246: NSD version 4.14.0 introduced a bug where a specially crafted APL RR, with an adflength larger than permitted

Routine

HIGH 8.1UPGRADE

CVE-2026-12246 is a high-severity flaw (CVSS 8.1) affecting nsd. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

NSD version 4.14.0 introduced a bug where a specially crafted APL RR, with an adflength larger than permitted for the address family will overwrite the stack when the zone is written to disk, with a maximum of 111 attacker controlled bytes.

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.1 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.4% (top 62%)
CISA exploited list	No
Weakness	CWE-20, CWE-120
Published	2026-06-25
Last modified	2026-10-25

Publisher (CNA): NLnet Labs · Vendor: nlnetlabs

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-25 07:16 UTCPublished CVE record published
2026-10-25 23:10 UTCUpdated Record last modified

nlnetlabs nsd UPGRADE

Affected: >= 4.14.0 and < 4.14.3

Fixed in: 4.14.3

Safe to downgrade to: a release before 4.14.0

1. Check installed version

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

2. UPGRADE to 4.14.3 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade nsd

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 4.14.0 (Debian / Ubuntu)

apt-cache madison nsd sudo apt install nsd=<VERSION_BEFORE_4.14.0> sudo apt-mark hold nsd

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

dnf --showduplicates list nsd sudo dnf downgrade nsd-<VERSION_BEFORE_4.14.0> sudo dnf versionlock add nsd

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-2026-12246?

nsd: upgrade to 4.14.3. Exact commands for each OS are on this page.

Is CVE-2026-12246 being exploited?

CVE-2026-12246 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-2026-12246 affect?

CVE-2026-12246 affects nsd. Severity is high (CVSS 8.1). NSD version 4.14.0 introduced a bug where a specially crafted APL RR, with an adflength larger than permitted for the address family will overwrite the stack when the zone is written to disk, with a maximum of 111 attacker controlled bytes.

How urgent is CVE-2026-12246?

Priority 38/100. High severity

Related CVEs

CVE-2026-12244 HIGH 8.8 UPGRADE If NSD is configured as secondary for a zone, the primary of that zone can crash NSD with an AXFR containing a
CVE-2026-12245 HIGH 7.5 UPGRADE NSD from version 4.13.0 has a heap use-after-free bug in logging errors on TLS connections, causing a crash of
CVE-2026-12490 HIGH 7.5 UPGRADE When a provide-xfr is given with a tls-auth-name, a secondary requesting a transfer should provide a client ce

References

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