Amazon Linux 2023 Security Advisory: ALAS2023-2025-1122
Advisory Released Date: 2025-08-08
Advisory Updated Date: 2025-08-08
Severity:
Important
Issue Overview:
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. (CVE-2025-5994)
Affected Packages:
unbound
Issue Correction:
Run dnf update unbound --releasever 2023.8.20250808 or dnf update --advisory ALAS2023-2025-1122 --releasever 2023.8.20250808 to update your system.
More information on how to update your system can be found on this page: Amazon Linux 2023 documentation
New Packages:
aarch64:
unbound-utils-1.17.1-1.amzn2023.0.8.aarch64
unbound-libs-debuginfo-1.17.1-1.amzn2023.0.8.aarch64
unbound-anchor-debuginfo-1.17.1-1.amzn2023.0.8.aarch64
unbound-debugsource-1.17.1-1.amzn2023.0.8.aarch64
unbound-libs-1.17.1-1.amzn2023.0.8.aarch64
unbound-devel-1.17.1-1.amzn2023.0.8.aarch64
python3-unbound-1.17.1-1.amzn2023.0.8.aarch64
python3-unbound-debuginfo-1.17.1-1.amzn2023.0.8.aarch64
unbound-debuginfo-1.17.1-1.amzn2023.0.8.aarch64
unbound-anchor-1.17.1-1.amzn2023.0.8.aarch64
unbound-utils-debuginfo-1.17.1-1.amzn2023.0.8.aarch64
unbound-1.17.1-1.amzn2023.0.8.aarch64
src:
unbound-1.17.1-1.amzn2023.0.8.src
x86_64:
unbound-debuginfo-1.17.1-1.amzn2023.0.8.x86_64
unbound-utils-debuginfo-1.17.1-1.amzn2023.0.8.x86_64
python3-unbound-debuginfo-1.17.1-1.amzn2023.0.8.x86_64
unbound-anchor-debuginfo-1.17.1-1.amzn2023.0.8.x86_64
unbound-libs-1.17.1-1.amzn2023.0.8.x86_64
unbound-debugsource-1.17.1-1.amzn2023.0.8.x86_64
unbound-devel-1.17.1-1.amzn2023.0.8.x86_64
unbound-libs-debuginfo-1.17.1-1.amzn2023.0.8.x86_64
unbound-anchor-1.17.1-1.amzn2023.0.8.x86_64
unbound-utils-1.17.1-1.amzn2023.0.8.x86_64
python3-unbound-1.17.1-1.amzn2023.0.8.x86_64
unbound-1.17.1-1.amzn2023.0.8.x86_64