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.
CVSS Details
- CVSS 4.0 Base Score: 8.7 (HIGH)
- CVSS 4.0 Vector: (CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:U/V:C/RE:X/U:X)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Alma_linux | — | Upgrade python3-unboundUpgrade unboundUpgrade unbound-develUpgrade unbound-dracutUpgrade unbound-libs | Jul 29, 2025 | Jul 28, 2025 |
| Alpine Linux | — | Upgrade unbound | Aug 8, 2025 | Jul 16, 2025 |
| Amazon Linux Ami 2 | — | Upgrade unbound-anchorUpgrade unbound-develUpgrade unbound-libsUpgrade python2-unboundUpgrade unboundUpgrade unbound-debuginfoUpgrade unbound-utilsUpgrade python3-unbound | May 20, 2026 | May 20, 2026 |
| Amazon_linux_2023 | — | Upgrade unbound-utils-debuginfoUpgrade unbound-anchor-debuginfoUpgrade unbound-libs-debuginfoUpgrade python3-unbound-debuginfoUpgrade unbound-debugsourceUpgrade unbound-anchorUpgrade unbound-develUpgrade unbound-libsUpgrade unbound-utilsUpgrade python3-unboundUpgrade unbound-debuginfoUpgrade unbound | Aug 5, 2025 | Jul 16, 2025 |
| Debian | — | Upgrade unbound | Jul 18, 2025 | Jul 16, 2025 |
| Freebsd | — | Upgrade unbound | Jul 19, 2025 | Jul 18, 2025 |
| Huawei Euleros 2_0_sp10 | — | Upgrade unbound-libsUpgrade python3-unboundUpgrade unbound | Nov 12, 2025 | Oct 10, 2025 |
| Huawei Euleros 2_0_sp11 | — | Upgrade unbound-libsUpgrade unboundUpgrade python3-unbound | Oct 14, 2025 | Oct 10, 2025 |
| Huawei Euleros 2_0_sp12 | — | Upgrade python3-unboundUpgrade unboundUpgrade unbound-libs | Nov 12, 2025 | Oct 10, 2025 |
| Huawei Euleros 2_0_sp13 | — | Upgrade unbound-libsUpgrade python3-unbound | Oct 24, 2025 | Oct 10, 2025 |
| Nutanix Ahv | — | Upgrade Nutanix AHV to the latest version | Jun 5, 2026 | Oct 10, 2025 |
| Oracle_linux | — | Upgrade unbound-develUpgrade unboundUpgrade unbound-libsUpgrade unbound-anchorUpgrade unbound-dracutUpgrade python3-unbound | Jul 29, 2025 | Jul 16, 2025 |
| Redhat Openshift | — | Upgrade rhcos | Aug 10, 2026 | Jul 16, 2025 |
| Redhat_linux | — | Upgrade unbound-debuginfoUpgrade unboundUpgrade unbound-libs-debuginfoUpgrade python3-unboundUpgrade unbound-anchorNo solution existsUpgrade unbound-develUpgrade python3-unbound-debuginfoUpgrade unbound-dracutUpgrade unbound-debugsourceUpgrade unbound-anchor-debuginfoUpgrade unbound-libsUpgrade unbound-utils-debuginfo | Jul 17, 2025 | Jul 16, 2025 |
| Rocky_linux | — | Upgrade unbound-libs-debuginfoUpgrade unbound-debuginfoUpgrade python3-unbound-debuginfoUpgrade unboundUpgrade unbound-libsUpgrade unbound-anchorUpgrade unbound-anchor-debuginfoUpgrade unbound-dracutUpgrade unbound-debugsourceUpgrade unbound-develUpgrade python3-unbound | Feb 5, 2026 | Oct 3, 2025 |
| Suse | — | Upgrade unboundUpgrade unbound-anchorUpgrade libunbound8Upgrade python3-unboundUpgrade unbound-devel | Nov 5, 2025 | Jul 29, 2025 |
| Ubuntu | — | Upgrade unboundUpgrade libunbound8 | Jul 23, 2025 | Jul 16, 2025 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | Feb 9, 2026 | Jul 16, 2025 |
Prioritise with Active Threat Intelligence
With curated Threat Intelligence, you can see which vulnerabilities truly put you at risk, prioritize what matters most, and act before attackers do.
Explore Intelligence Hub