AmazonAnalysisAWS issues security advisory for Linux kernel IPv4 TCP use-after-free flaw
What happened.Amazon Web Services published security bulletin ALAS2-2026-4065 warning customers of a critical use-after-free vulnerability discovered within the Linux kernel IPv4 network stack.
Why it matters.Core networking protocol handlers operate at the highest privilege level within cloud hypervisor hosts and guest runtimes. When remote packet processing contains heap allocation defects, network-facing instances face unexpected kernel panics and unauthorized code execution. Infrastructure engineers should review production fleet inventories to identify unpatched kernel versions. DevOps operators must schedule rolling reboots across EC2 and Lightsail instances to complete patch application.
The technical specifications:
- Vulnerability mechanics: Tracked under CVE-2026-98432 with a maximum CVSS rating of 9.8, a race condition in TCP connection handling allows remote unauthenticated actors to trigger memory corruption.
- Exploitation path: An adversary transmits specially crafted IPv4 TCP packets during handshake negotiation, forcing race conditions in connection state teardown that destabilize host kernel execution.
- Remediation releases: AWS rolled out updated kernel packages across Amazon Linux 2 and Amazon Linux 2023, advising platform operators that instance reboots are mandatory to apply mitigations.