OVSwrap (CVE-2026-64531): AI-Assisted Discovery of a Linux Kernel LPE

Researchers used LLM-based agents equipped with graph-reasoning tools and persistent ASCII-diagram tracking of memory layouts to uncover OVSwrap (CVE-2026-64531), a local privilege escalation bug in the Linux kernel's Open vSwitch (OVS) datapath implementation.

The flaw stems from a 16-bit Netlink attribute length field (nla_len) used to store the size of nested OVS actions such as CLONE. When an attacker submits deeply nested actions that expand past 65,535 bytes, the length wraps around to a small value, and later parsing code resumes reading from an incorrect, attacker-controlled offset inside the same buffer. Because this offset is deterministic once kernel build details are known, exploitation requires no heap grooming, making the bug behave more like a reliable logic flaw than a typical memory-safety issue.

The vulnerability is reachable by any unprivileged user via unshare -Urn, since Open vSwitch's Generic Netlink families are namespace-aware and can be auto-loaded as kernel modules. This leaves most distributions that enable unprivileged user namespaces and ship OVS as a loadable module vulnerable by default, with potential implications for container escape scenarios as well.

The issue was reported to kernel and OVS maintainers in June 2026, patched in stable kernels by July 24, and disclosed on July 28, 2026 under coordinated embargo with linux-distros. A defense-in-depth 32 KiB action-size limit that had masked this bug class for over a decade was removed in March 2025, exposing the wraparound.