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OpenAdvisories
Low · 3.7 CVE-2026-54478 EUVD-2026-47678GHSA-pp7x-83x2-99v7

DNS Cookie bypass when combined with proxy-protocol use

Published Jul 22, 2026 · Updated Jul 22, 2026 · Assigned by NLnet Labs

Vendor: NLnet Labs Product: Unbound Package: unbound Package: unbound Package: unbound Package: unbound Ecosystem: Alpine Ecosystem: Azure Linux Ecosystem: Debian Ecosystem: Ubuntu

Description

In NLnet Labs Unbound 1.18.0 up to and including 1.25.1, when Unbound listens on a 'proxy-protocol-port' interface with 'answer-cookie: yes', the RFC 9018 server-cookie SipHash is computed over the proxy's wire address instead of the PROXYv2-declared client. One server cookie obtained through a given proxy node therefore validates for every PROXYv2-declared source behind that node. On a UDP+proxy-protocol front, an off-path attacker can harvest one cookie with a single legitimate query, then replay it under any spoofed source and pass DNS Cookie checks that were deployed to defeat this in the first place.

Affected products

VendorProductAffectedFixed
NLnet Labs Unbound 1.18.0 – < 1.25.2 1.25.2

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

Debian

Security tracker ↗
ReleasePackageFixed inAdvisory
Debian 14 unbound 1.25.2-1 —
Debian 13 unbound 1.26.1-0+deb13u1 —
Debian 12 unbound No fix yet —

Ubuntu

Security tracker ↗
ReleasePackageFixed inAdvisory
Ubuntu 26.10 unbound No fix yet —
Ubuntu 26.04 LTS unbound No fix yet —
Ubuntu 24.04 LTS unbound No fix yet —
Ubuntu 22.04 LTS unbound No fix yet —
Show 4 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Ubuntu Pro 20.04 LTS unbound No fix yet —
Ubuntu Pro 18.04 LTS unbound No fix yet —
Ubuntu Pro 16.04 LTS unbound No fix yet —
Ubuntu Pro 14.04 LTS unbound No fix yet —

Red Hat

Security tracker ↗
ReleasePackageFixed inAdvisory
RHEL 10 unbound +6 1.26.1-2.el10_3 RHSA-2026:97121
RHEL 9 unbound +4 1.26.1-1.el9_9 RHSA-2026:97497
Show 1 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Red Hat Hardened Images 1 unbound +7 1.25.2-0.1.hum1 RHSA-2026:43588

Rocky Linux

Errata ↗
ReleasePackageFixed inAdvisory
Rocky Linux 10 unbound +6 1.26.1-2.el10_3 RLSA-2026:97121
Rocky Linux 9 unbound +4 1.26.1-1.el9_9 RLSA-2026:97497

SUSE

Security tracker ↗
ReleasePackageFixed inAdvisory
SLES 15 SP7 unbound 1.25.2-150600.23.19.1 SUSE-SU-2026:3885-1
SLES 15 SP6 unbound 1.25.2-150600.23.19.1 SUSE-SU-2026:3885-1
SLES 15 SP5 unbound 1.25.2-150100.10.28.1 SUSE-SU-2026:3884-1
SLES 15 SP4 unbound 1.25.2-150100.10.28.1 SUSE-SU-2026:3884-1
Show 11 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
SLES for SAP 16.0 unbound 1.25.2-160000.1.1 SUSE-SU-2026:23226-1, SUSE-SU-2026:23215-1
SLES for SAP 15 SP6 unbound 1.25.2-150600.23.19.1 SUSE-SU-2026:3885-1
SLES for SAP 15 SP5 unbound 1.25.2-150100.10.28.1 SUSE-SU-2026:3884-1
SLES for SAP 15 SP4 unbound 1.25.2-150100.10.28.1 SUSE-SU-2026:3884-1
SLES 16.0 unbound 1.25.2-160000.1.1 SUSE-SU-2026:23226-1, SUSE-SU-2026:23215-1
SLE Micro 6.2 unbound 1.25.2-160000.1.1 SUSE-SU-2026:23050-1
SLE Micro 6.1 unbound 1.25.2-slfo.1.1_1.1 SUSE-SU-2026:23349-1
SLE Micro 6.0 unbound 1.25.2-1.1 SUSE-SU-2026:23360-1
SLE Micro 5.5 unbound 1.25.2-150100.10.28.1 SUSE-SU-2026:3884-1
SLE HPC 15 SP5 unbound 1.25.2-150100.10.28.1 SUSE-SU-2026:3884-1
SLE HPC 15 SP4 unbound 1.25.2-150100.10.28.1 SUSE-SU-2026:3884-1

openSUSE

Security tracker ↗
ReleasePackageFixed inAdvisory
openSUSE Tumbleweed unbound 1.25.2-1.1 openSUSE-SU-2026:11380-1
openSUSE Leap 16.0 unbound 1.25.2-160000.1.1 openSUSE-SU-2026:21550-1

Alpine

Security tracker ↗
ReleasePackageFixed inAdvisory
Alpine v3.24 unbound 1.25.2-r0 —
Alpine v3.23 unbound 1.25.2-r0 —
Alpine v3.22 unbound 1.25.2-r0 —

Azure Linux

ReleasePackageFixed inAdvisory
Azure Linux 3 unbound 1.25.2-1 —

Advisories 16

References