Description
A multi-vendor cache poisoning vulnerability named 'Rebirthday Attack' has been discovered in caching resolvers that support EDNS Client Subnet (ECS). Unbound is also vulnerable when compiled with ECS support, i.e., '--enable-subnet', AND configured to send ECS information along with queries to upstream name servers, i.e., at least one of the 'send-client-subnet', 'client-subnet-zone' or 'client-subnet-always-forward' options is used. Resolvers supporting ECS need to segregate outgoing queries to accommodate for different outgoing ECS information. This re-opens up resolvers to a birthday paradox attack (Rebirthday Attack) that tries to match the DNS transaction ID in order to cache non-ECS poisonous replies.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| NLnet Labs | Unbound | 1.6.2 – < 1.23.0 | 1.23.0 |
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 | 1.22.0-2 | — |
| Debian 13 | unbound | 1.22.0-2 | — |
| Debian 12 | unbound | 1.17.1-2+deb12u3 | DSA-5987-1 |
| Debian 11 | unbound | 1.13.1-1+deb11u5 | DLA-4280-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 25.10 | unbound | 1.22.0-2ubuntu1 | — |
| Ubuntu 24.04 LTS | unbound | 1.19.2-1ubuntu3.5 | USN-7666-1 |
| Ubuntu 22.04 LTS | unbound | 1.13.1-1ubuntu5.11 | USN-7666-1 |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| 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 ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 10 | unbound +5 | 1.20.0-12.el10_0 | RHSA-2025:12064 |
| RHEL 9 | unbound +4 | 1.16.2-19.el9_6.1 | RHSA-2025:11849 |
| RHEL 8 | unbound +3 | 1.16.2-5.9.el8_10 | RHSA-2025:11884 |
Show 11 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 9.4 EUS | unbound +3 | 1.16.2-8.el9_4.2 | RHSA-2025:12416 |
| RHEL 9.2 E4S | unbound +2 | 1.16.2-3.el9_2.5 | RHSA-2025:12523 |
| RHEL 9.0 E4S | unbound +2 | 1.13.1-13.el9_0.5 | RHSA-2025:12520 |
| RHEL 8.8 TUS | unbound +3 | 1.16.2-5.el8_8.5 | RHSA-2025:12929 |
| RHEL 8.8 E4S | unbound +3 | 1.16.2-5.el8_8.5 | RHSA-2025:12929 |
| RHEL 8.6 TUS | unbound +3 | 1.7.3-17.el8_6.6 | RHSA-2025:13577 |
| RHEL 8.6 E4S | unbound +3 | 1.7.3-17.el8_6.6 | RHSA-2025:13577 |
| RHEL 8.6 AUS | unbound +3 | 1.7.3-17.el8_6.6 | RHSA-2025:13577 |
| RHEL 8.4 EUS Long Life | unbound +3 | 1.7.3-15.el8_4.2 | RHSA-2025:13575 |
| RHEL 8.4 AUS | unbound +3 | 1.7.3-15.el8_4.2 | RHSA-2025:13575 |
| RHEL 8.2 AUS | unbound +3 | 1.7.3-12.el8_2.2 | RHSA-2025:13576 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 10 | unbound +5 | 1.20.0-12.el10_0 | ALSA-2025:12064 |
| AlmaLinux 9 | unbound +4 | 1.16.2-19.el9_6.1 | ALSA-2025:11849 |
| AlmaLinux 8 | unbound +3 | 1.16.2-5.9.el8_10 | ALSA-2025:11884 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 9 | unbound | 1.16.2-19.el9_6.1 | RLSA-2025:11849 |
| Rocky Linux 8 | unbound | 1.16.2-5.9.el8 | RLSA-2025:11884 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | unbound | 1.23.1-1.1 | openSUSE-SU-2025:15435-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | unbound | 1.23.1-r0 | — |
| Alpine v3.23 | unbound | 1.23.1-r0 | — |
| Alpine v3.22 | unbound | 1.23.1-r0 | — |
| Alpine v3.21 | unbound | 1.22.0-r1 | — |
| Alpine v3.20 | unbound | 1.20.0-r2 | — |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | unbound | 1.20.0-r2 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | unbound +5 | 1.17.1-1.amzn2023.0.8 | ALAS2023-2025-1122 |
| Amazon Linux 2 | unbound +4 | 1.7.3-15.amzn2.0.10 | ALAS2-2025-2951 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 10 | unbound +5 | 1.20.0-12.el10_0 | ELSA-2025-12064 |
| Oracle Linux 9 | unbound +4 | 1.16.2-19.el9_6.1 | ELSA-2025-11849 |
| Oracle Linux 8 | unbound +3 | 1.16.2-5.9.el8_10 | ELSA-2025-11884 |
Advisories 27
- ALSA-2025:12064 Important: unbound security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2025:11849 Important: unbound security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2025:11884 Important: unbound security update AlmaLinux Security Advisories · Oct 29, 2026
- WID-SEC-2026-0489 Xerox FreeFlow Print Server: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff BSI CERT-Bund (WID) · Oct 21, 2026
- RHSA-2025:13576 Red Hat Security Advisory: unbound security update Red Hat Security Advisories (RHSA) · Oct 15, 2026
- RHSA-2025:13577 Red Hat Security Advisory: unbound security update Red Hat Security Advisories (RHSA) · Oct 15, 2026
- RHSA-2025:13575 Red Hat Security Advisory: unbound security update Red Hat Security Advisories (RHSA) · Oct 15, 2026
- RHSA-2025:12929 Red Hat Security Advisory: unbound security update Red Hat Security Advisories (RHSA) · Oct 15, 2026
- RHSA-2025:12523 Red Hat Security Advisory: unbound security update Red Hat Security Advisories (RHSA) · Oct 15, 2026
- RHSA-2025:12520 Red Hat Security Advisory: unbound security update Red Hat Security Advisories (RHSA) · Oct 15, 2026
- RHSA-2025:12416 Red Hat Security Advisory: unbound security update Red Hat Security Advisories (RHSA) · Oct 15, 2026
- RHSA-2025:12064 Red Hat Security Advisory: unbound security update Red Hat Security Advisories (RHSA) · Oct 15, 2026
- RHSA-2025:11884 Red Hat Security Advisory: unbound security update Red Hat Security Advisories (RHSA) · Oct 15, 2026
- RHSA-2025:11849 Red Hat Security Advisory: unbound security update Red Hat Security Advisories (RHSA) · Oct 15, 2026
- WID-SEC-2025-1656 Red Hat Enterprise Linux (unbound): Schwachstelle ermöglicht Manipulation von Daten BSI CERT-Bund (WID) · Sep 27, 2026
- RLSA-2025:11884 Important: unbound security update Rocky Linux Security Advisories · May 29, 2026
- USN-7666-1 unbound vulnerabilities Ubuntu Security Notices (USN) · Apr 27, 2026
- openSUSE-SU-2025:15435-1 libunbound8-1.23.1-1.1 on GA media SUSE / openSUSE Security Updates · Mar 23, 2026
- DSA-5987-1 unbound - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-4280-1 unbound - security update Debian Security (DSA / DLA) · Mar 9, 2026
- RLSA-2025:11849 Important: unbound security update Rocky Linux Security Advisories · Oct 7, 2025
- WID-SEC-2025-2043 IBM QRadar SIEM: Mehrere Schwachstellen BSI CERT-Bund (WID) · Oct 1, 2025
- ALAS2023-2025-1122 Important: unbound security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Aug 8, 2025
- ALAS2-2025-2951 Important: unbound security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Aug 4, 2025
- ELSA-2025-12064 Important: unbound security update (Oracle Linux 10) Oracle Linux Security Advisories (ELSA) · Jul 29, 2025
- ELSA-2025-11849 Important: unbound security update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · Jul 28, 2025
- ELSA-2025-11884 Important: unbound security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Jul 28, 2025
References
- https://nlnetlabs.nl/downloads/unbound/CVE-2025-5994.txt vendor-advisory