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CVE-2026-72137 is a double-free vulnerability in the Linux kernel XFRM subsystem's NAT keepalive handling. On an IPv4 or IPv6 packet-send error, nat_keepalive_send() could free a socket buffer after the applicable output helper had accepted ownership of it. Because the networking output path may already have consumed the buffer before returning an error, the additional cleanup could free the same buffer a second time. The issue affects kernel versions containing the vulnerable NAT keepalive code introduced in June 2024 and was resolved upstream in July 2026 by moving pre-handoff failure cleanup into the IPv4 and IPv6 helper functions while retaining only dispatch and unsupported-family cleanup in nat_keepalive_send().
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A critical (CVSS 9.8) Linux kernel double-free vulnerability in the xfrm nat_keepalive component. An error path can free an skb after the networking output stack has already consumed it, causing memory corruption and enabling local root privilege escalation.
A Linux kernel XFRM nat_keepalive double-free vulnerability triggered on a send error. It is rated CVSS v3.1 4.1 (Medium) by Amazon Linux, with a local attack vector, high attack complexity, high privileges required, and potential high availability impact.
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Cross-references every affected SKU, including bundled OEM variants.
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