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 unbound-dracutUpgrade unboundUpgrade unbound-develUpgrade python3-unboundUpgrade 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 unboundUpgrade python2-unboundUpgrade unbound-develUpgrade unbound-libsUpgrade unbound-debuginfoUpgrade unbound-utilsUpgrade python3-unbound | May 20, 2026 | May 20, 2026 |
| Amazon_linux_2023 | — | Upgrade unbound-anchorUpgrade unbound-debuginfoUpgrade unbound-libsUpgrade unboundUpgrade python3-unboundUpgrade unbound-develUpgrade unbound-utilsUpgrade unbound-libs-debuginfoUpgrade unbound-utils-debuginfoUpgrade unbound-anchor-debuginfoUpgrade python3-unbound-debuginfoUpgrade unbound-debugsource | 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 unboundUpgrade python3-unboundUpgrade unbound-libs | Nov 12, 2025 | Oct 10, 2025 |
| Huawei Euleros 2_0_sp11 | — | Upgrade python3-unboundUpgrade unbound-libsUpgrade unbound | Oct 14, 2025 | Oct 10, 2025 |
| Huawei Euleros 2_0_sp12 | — | Upgrade unboundUpgrade python3-unboundUpgrade unbound-libs | Nov 12, 2025 | Oct 10, 2025 |
| Huawei Euleros 2_0_sp13 | — | Upgrade python3-unboundUpgrade unbound-libs | Oct 24, 2025 | Oct 10, 2025 |
| Nutanix Ahv | — | Upgrade Nutanix AHV to the latest version | Jun 5, 2026 | Oct 10, 2025 |
| Oracle_linux | — | Upgrade unboundUpgrade unbound-develUpgrade unbound-anchorUpgrade unbound-libsUpgrade unbound-dracutUpgrade python3-unbound | Jul 29, 2025 | Jul 16, 2025 |
| Redhat Openshift | — | Upgrade rhcos | Aug 10, 2026 | Jul 16, 2025 |
| Redhat_linux | — | Upgrade python3-unbound-debuginfoUpgrade unbound-utils-debuginfoUpgrade unbound-debugsourceUpgrade unbound-develUpgrade unbound-anchor-debuginfoUpgrade unbound-libsUpgrade unbound-dracutUpgrade unbound-libs-debuginfoUpgrade unbound-anchorUpgrade unboundUpgrade python3-unboundUpgrade unbound-debuginfoNo solution exists | Jul 17, 2025 | Jul 16, 2025 |
| Rocky_linux | — | Upgrade python3-unboundUpgrade unbound-develUpgrade unbound-debugsourceUpgrade unbound-anchorUpgrade unbound-libs-debuginfoUpgrade unbound-libsUpgrade unbound-dracutUpgrade unbound-anchor-debuginfoUpgrade unboundUpgrade python3-unbound-debuginfoUpgrade unbound-debuginfo | Feb 5, 2026 | Oct 3, 2025 |
| Suse | — | Upgrade unbound-develUpgrade python3-unboundUpgrade libunbound8Upgrade unboundUpgrade unbound-anchor | 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 |
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