Description
A vulnerability named 'Non-Responsive Delegation Attack' (NRDelegation Attack) has been discovered in various DNS resolving software. The NRDelegation Attack works by having a malicious delegation with a considerable number of non responsive nameservers. The attack starts by querying a resolver for a record that relies on those unresponsive nameservers. The attack can cause a resolver to spend a lot of time/resources resolving records under a malicious delegation point where a considerable number of unresponsive NS records reside. It can trigger high CPU usage in some resolver implementations that continually look in the cache for resolved NS records in that delegation. This can lead to degraded performance and eventually denial of service in orchestrated attacks. Unbound does not suffer from high CPU usage, but resources are still needed for resolving the malicious delegation. Unbound will keep trying to resolve the record until hard limits are reached. Based on the nature of the attack and the replies, different limits could be reached. From version 1.16.3 on, Unbound introduces fixes for better performance when under load, by cutting opportunistic queries for nameserver discovery and DNSKEY prefetching and limiting the number of times a delegation point can issue a cache lookup for missing records.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| NLnet Labs | Unbound | unspecified – ≤ 1.16.2 | — |
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 ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | unbound | 1.16.3-1 | — |
| Debian 13 | unbound | 1.16.3-1 | — |
| Debian 12 | unbound | 1.16.3-1 | — |
| Debian 10 | unbound | 1.9.0-2+deb10u3 | DLA-3371-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 22.04 LTS | unbound | 1.13.1-1ubuntu5.3 | USN-5732-1 |
| Ubuntu 20.04 LTS | unbound | 1.9.4-2ubuntu1.4 | USN-5732-1 |
| Ubuntu 18.04 LTS | unbound | 1.6.7-1ubuntu2.6 | USN-5732-1 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 16.04 LTS | unbound | No fix yet | — |
| Ubuntu Pro 14.04 LTS | unbound | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 9 | unbound +3 | 1.16.2-3.el9 | RHSA-2023:2370 |
| RHEL 8 | unbound +3 | 1.16.2-5.el8 | RHSA-2023:2771 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8.6 EUS | unbound +3 | 1.7.3-17.el8_6.5 | RHSA-2024:2045 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 9 | unbound +3 | 1.16.2-3.el9 | ALSA-2023:2370 |
| AlmaLinux 8 | unbound +3 | 1.16.2-5.el8 | ALSA-2023:2771 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | unbound | 1.16.2-5.12.el8_10 | RLSA-2023:2771 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP6 | unbound | 1.20.0-150600.23.3.1 | SUSE-SU-2024:1923-1 |
| SLES 15 SP5 | unbound | 1.20.0-150100.10.13.1 | SUSE-SU-2024:1991-1 |
| SLES 15 SP4 | unbound | 1.20.0-150100.10.13.1 | SUSE-SU-2024:1991-1 |
| SLES 15 SP3 | unbound | 1.20.0-150100.10.13.1 | SUSE-SU-2024:1991-1 |
| SLES 15 SP2 | unbound | 1.20.0-150100.10.13.1 | SUSE-SU-2024:1991-1 |
Show 10 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 15 SP4 | unbound | 1.20.0-150100.10.13.1 | SUSE-SU-2024:1991-1 |
| SLES for SAP 15 SP3 | unbound | 1.20.0-150100.10.13.1 | SUSE-SU-2024:1991-1 |
| SLES for SAP 15 SP2 | unbound | 1.20.0-150100.10.13.1 | SUSE-SU-2024:1991-1 |
| SLE Micro 5.5 | unbound | 1.20.0-150100.10.13.1 | SUSE-SU-2024:1991-2, SUSE-SU-2024:1991-1 |
| SLE HPC 15 SP4 | unbound | 1.20.0-150100.10.13.1 | SUSE-SU-2024:1991-1 |
| SLE HPC 15 SP3 | unbound | 1.20.0-150100.10.13.1 | SUSE-SU-2024:1991-1 |
| SLE HPC 15 SP2 | unbound | 1.20.0-150100.10.13.1 | SUSE-SU-2024:1991-1 |
| SUSE Manager Server 4.3 | unbound | 1.20.0-150100.10.13.1 | SUSE-SU-2024:1991-1 |
| SUSE Manager Proxy 4.3 | unbound | 1.20.0-150100.10.13.1 | SUSE-SU-2024:1991-1 |
| SUSE Enterprise Storage 7.1 | unbound | 1.20.0-150100.10.13.1 | SUSE-SU-2024:1991-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | unbound | 1.16.3-1.1 | openSUSE-SU-2024:12368-1 |
| openSUSE Leap 15.6 | unbound | 1.20.0-150600.23.3.1 | SUSE-SU-2024:1923-1 |
| openSUSE Leap 15.5 | unbound | 1.20.0-150100.10.13.1 | SUSE-SU-2024:1991-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | unbound | 1.16.3-r0 | — |
| Alpine v3.23 | unbound | 1.16.3-r0 | — |
| Alpine v3.22 | unbound | 1.16.3-r0 | — |
| Alpine v3.21 | unbound | 1.16.3-r0 | — |
| Alpine v3.20 | unbound | 1.16.3-r0 | — |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | unbound | 1.16.3-r0 | — |
| Alpine v3.18 | unbound | 1.16.3-r0 | — |
| Alpine v3.17 | unbound | 1.16.3-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | unbound +5 | 1.16.3-2.amzn2023.0.1 | ALAS2023-2023-078 |
| Amazon Linux 2 | unbound +4 | 1.7.3-15.amzn2.0.6 | ALAS2-2024-2467 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 2 (CBL-Mariner) | unbound | 1.16.3-1 | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 9 | unbound +3 | 1.16.2-3.el9 | ELSA-2023-2370 |
| Oracle Linux 8 | unbound +3 | 1.16.2-5.el8 | ELSA-2023-2771 |
Advisories 19
- ALSA-2023:2370 Moderate: unbound security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2023:2771 Moderate: unbound security and bug fix update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2024:2045 Red Hat Security Advisory: unbound security update Red Hat Security Advisories (RHSA) · Aug 5, 2026
- RHSA-2023:2771 Red Hat Security Advisory: unbound security and bug fix update Red Hat Security Advisories (RHSA) · Aug 5, 2026
- RHSA-2023:2370 Red Hat Security Advisory: unbound security update Red Hat Security Advisories (RHSA) · Aug 5, 2026
- RLSA-2023:2771 Moderate: unbound security and bug fix update Rocky Linux Security Advisories · Aug 4, 2026
- WID-SEC-2023-1185 Red Hat Enterprise Linux: Mehrere Schwachstellen BSI CERT-Bund (WID) · Aug 3, 2026
- USN-5732-1 unbound vulnerability Ubuntu Security Notices (USN) · Apr 27, 2026
- DLA-3371-1 unbound - security update Debian Security (DSA / DLA) · Mar 9, 2026
- SUSE-SU-2024:1923-1 Security update for unbound SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:12368-1 libunbound8-1.16.3-1.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2024:1991-1 Security update for unbound SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2024:1991-2 Security update for unbound SUSE / openSUSE Security Updates · May 2, 2025
- ALAS2-2024-2467 Moderate: unbound security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Feb 19, 2024
- ICSA-23-234-01 Hitachi Energy AFF66x CISA ICS & IT advisories · Aug 22, 2023
- ELSA-2023-2771 Moderate: unbound security and bug fix update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · May 24, 2023
- WID-SEC-2023-0561 Xerox FreeFlow Print Server: Mehrere Schwachstellen BSI CERT-Bund (WID) · May 18, 2023
- ELSA-2023-2370 Moderate: unbound security update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · May 15, 2023
- ALAS2023-2023-078 Moderate: unbound security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Feb 22, 2023
References
- https://www.nlnetlabs.nl/downloads/unbound/CVE-2022-3204.txt
- FEDORA-2022-1326d2815c vendor-advisory
- FEDORA-2022-164cf7837e vendor-advisory
- FEDORA-2022-204ee3da84 vendor-advisory
- GLSA-202212-02 vendor-advisory
- [debian-lts-announce] 20230329 [SECURITY] [DLA 3371-1] unbound security update mailing-list