CVE-2026-32665: In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, when downstream DNS-over-QUIC (DoQ) is enabled, the f

Routine

HIGH 7.5REMOTEUPGRADE

CVE-2026-32665 is a high-severity flaw (CVSS 7.5) affecting unbound. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, when downstream DNS-over-QUIC (DoQ) is enabled, the first two bidirectional streams on a new QUIC connection (stream_id 0 and 4) bypass the per-stream 'quic-size' gate entirely, and large input buffers are allocated later, after only the 2-byte length prefix has been received from the initial streams. As a result, a remote client can make Unbound exceed the configured 'quic-size' limit with

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 80%)
CISA exploited list	No
Weakness	CWE-1284
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: >= 1.22.0 and < 1.25.2

Fixed in: 1.25.2

Safe to downgrade to: a release before 1.22.0

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 1.22.0 (Debian / Ubuntu)

apt-cache madison unbound sudo apt install unbound=<VERSION_BEFORE_1.22.0> 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_1.22.0> 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.

Exact fixes by distribution

Fedora 46 · sugar-toolkit-gtk3 · FIXED · 0.122-2.fc46 · FEDORA-2026-d11eb2faf0 · source

sudo dnf upgrade --advisory=FEDORA-2026-d11eb2faf0

Fedora ELN · ntpd-rs · FIXED · 1.7.2-3.eln159 · FEDORA-2026-57e4a99310 · source

sudo dnf upgrade --advisory=FEDORA-2026-57e4a99310

Ubuntu 20.04 · unbound · NOT AFFECTED

Ubuntu 22.04 · unbound · NOT AFFECTED

Ubuntu 24.04 · unbound · NOT AFFECTED

Debian 12 · unbound · NO FIX YET

Debian 13 · unbound · FIXED · 1.26.1-0+deb13u1

sudo apt update && sudo apt install --only-upgrade unbound dpkg --compare-versions "$(dpkg-query -W -f='${Version}' unbound)" ge "1.26.1-0+deb13u1" && echo PATCHED || echo STILL-VULNERABLE

RHEL 10 · unbound · NOT AFFECTED

RHEL 6 · unbound · NOT AFFECTED

RHEL 7 · unbound · NOT AFFECTED

RHEL 8 · unbound · NOT AFFECTED

RHEL 9 · unbound · NOT AFFECTED

Alpine 3.22 · unbound · NOT AFFECTED

Alpine 3.23 · unbound · NOT AFFECTED

Alpine 3.24 · unbound · NOT AFFECTED

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-2026-32665?

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

Is CVE-2026-32665 being exploited?

CVE-2026-32665 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-2026-32665 affect?

CVE-2026-32665 affects unbound. Severity is high (CVSS 7.5). In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, when downstream DNS-over-QUIC (DoQ) is enabled, the first two bidirectional streams on a new QUIC connection (stream_id 0 and 4) bypass the per-stream 'quic-size' gate entirely, and l

How urgent is CVE-2026-32665?

Priority 36/100. High severity; Remotely exploitable, no login, no user action

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References

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