Description
NLnet Labs Unbound 1.14.0 up to and including version 1.25.0 has a vulnerability that results in heap overflow when encoding multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options in the reply packet. The relevant options ('nsid', 'answer-cookie', 'pad-responses' (default)) need to be enabled for the vulnerability to be exploited. An adversary who can query Unbound can exploit the vulnerability by attaching multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options to the query. A flaw in the size calculation of the EDNS field truncates the correct value which allows the encoder to overflow the available space when writing. Those two combined lead to a heap overflow write of Unbound controlled data and eventually a crash. Unbound 1.25.1 contains a patch with a fix to de-duplicate the EDNS options and a fix to prevent truncation of the EDNS field size calculation.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| NLnet Labs | Unbound | 1.14.0 – < 1.25.1 | 1.25.1 |
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 ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | unbound | 1.25.1-1 | — |
| Debian 13 | unbound | 1.22.0-2+deb13u3 | — |
| Debian 12 | unbound | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.04 LTS | unbound | 1.24.2-1ubuntu2.1 | — |
| Ubuntu 25.10 | unbound | 1.22.0-2ubuntu2.3 | — |
| Ubuntu 24.04 LTS | unbound | 1.19.2-1ubuntu3.8 | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 10 | unbound +6 | 1.24.2-7.el10_2.1 | RHSA-2026:23231 |
| RHEL 9 | unbound +4 | 1.24.2-3.el9_8.1 | RHSA-2026:24369 |
| RHEL 8 | unbound +3 | 1.16.2-5.11.el8_10 | RHSA-2026:24365 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat Hardened Images 1 | unbound +7 | 1.25.1-0.1.hum1 | RHSA-2026:19752 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 10 | unbound +6 | 1.24.2-7.el10_2.1 | ALSA-2026:23231 |
| AlmaLinux 9 | unbound +4 | 1.24.2-3.el9_8.1 | ALSA-2026:24369 |
| AlmaLinux 8 | unbound +3 | 1.16.2-5.11.el8_10 | ALSA-2026:24365 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 10 | unbound | 1.24.2-7.el10_2.1 | RLSA-2026:23231 |
| Rocky Linux 9 | unbound | 1.24.2-3.el9_8.1 | RLSA-2026:24369 |
| Rocky Linux 8 | unbound | 1.16.2-5.11.el8_10 | RLSA-2026:24365 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP5 | unbound | 1.20.0-150100.10.25.1 | SUSE-SU-2026:2369-1 |
| SLES 15 SP4 | unbound | 1.20.0-150100.10.25.1 | SUSE-SU-2026:2369-1 |
Show 8 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 16.0 | unbound | 1.24.1-160000.2.1 | SUSE-SU-2026:22160-1 |
| SLES for SAP 15 SP5 | unbound | 1.20.0-150100.10.25.1 | SUSE-SU-2026:2369-1 |
| SLES for SAP 15 SP4 | unbound | 1.20.0-150100.10.25.1 | SUSE-SU-2026:2369-1 |
| SLES 16.0 | unbound | 1.24.1-160000.2.1 | SUSE-SU-2026:22160-1 |
| SLE Micro 6.2 | unbound | 1.24.1-160000.2.1 | SUSE-SU-2026:22213-1 |
| SLE Micro 5.5 | unbound | 1.20.0-150100.10.25.1 | SUSE-SU-2026:2369-1 |
| SLE HPC 15 SP5 | unbound | 1.20.0-150100.10.25.1 | SUSE-SU-2026:2369-1 |
| SLE HPC 15 SP4 | unbound | 1.20.0-150100.10.25.1 | SUSE-SU-2026:2369-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | unbound | 1.25.1-1.1 | openSUSE-SU-2026:10903-1 |
| openSUSE Leap 16.0 | unbound | 1.24.1-160000.2.1 | openSUSE-SU-2026:21083-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | unbound | 1.25.1-r0 | — |
| Alpine v3.23 | unbound | 1.25.2-r0 | — |
| Alpine v3.22 | unbound | 1.25.2-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | unbound +5 | 1.17.1-1.amzn2023.0.12 | ALAS2023-2026-1756 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | unbound | 1.25.1-1 | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 10 | unbound +6 | 1.24.2-7.el10_2.2 | ELSA-2026-23231 |
| Oracle Linux 9 | unbound +4 | 1.24.2-3.el9_8.1 | ELSA-2026-24369 |
| Oracle Linux 8 | unbound +3 | 1.16.2-5.11.el8_10 | ELSA-2026-24365 |
Advisories 21
- WID-SEC-2026-2455 Oracle Solaris Drittanbieterkomponenten: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 12, 2026
- WID-SEC-2026-1599 Unbound: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 10, 2026
- ALSA-2026:24369 Important: unbound security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2026:23231 Important: unbound security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2026:24365 Important: unbound security update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2026:24369 Red Hat Security Advisory: unbound security update Red Hat Security Advisories (RHSA) · Oct 19, 2026
- RHSA-2026:24365 Red Hat Security Advisory: unbound security update Red Hat Security Advisories (RHSA) · Oct 19, 2026
- RHSA-2026:23231 Red Hat Security Advisory: unbound security update Red Hat Security Advisories (RHSA) · Oct 19, 2026
- RHSA-2026:19752 Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update Red Hat Security Advisories (RHSA) · Oct 6, 2026
- ELSA-2026-23231 Important: unbound security update (Oracle Linux 10) Oracle Linux Security Advisories (ELSA) · Jul 21, 2026
- openSUSE-SU-2026:21083-1 Security update for unbound SUSE / openSUSE Security Updates · Jun 30, 2026
- SUSE-SU-2026:22160-1 Security update for unbound SUSE / openSUSE Security Updates · Jun 24, 2026
- SUSE-SU-2026:22213-1 Security update for unbound SUSE / openSUSE Security Updates · Jun 24, 2026
- ELSA-2026-24369 Important: unbound security update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · Jun 23, 2026
- SUSE-SU-2026:2369-1 Security update for unbound SUSE / openSUSE Security Updates · Jun 12, 2026
- RLSA-2026:24369 Important: unbound security update Rocky Linux Security Advisories · Jun 11, 2026
- RLSA-2026:24365 Important: unbound security update Rocky Linux Security Advisories · Jun 11, 2026
- ELSA-2026-24365 Important: unbound security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Jun 8, 2026
- RLSA-2026:23231 Important: unbound security update Rocky Linux Security Advisories · Jun 6, 2026
- openSUSE-SU-2026:10903-1 libunbound8-1.25.1-1.1 on GA media SUSE / openSUSE Security Updates · May 30, 2026
- ALAS2023-2026-1756 Important: unbound security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · May 26, 2026
References
- https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42944.txt vendor-advisory