CVE-2026-72137
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk10th percentile - higher than 10% of all known CVEs
Summary
In the Linux kernel, the xfrm module has a double-free issue in nat_keepalive_send(). When the IPv4 or IPv6 helper reports an error, the keepalive packet is freed, but if the packet has already been handed to the network stack, it may be freed again, leading to unsafe operation.
Risk Assessment
Double-free can lead to memory corruption, potentially allowing code execution or causing a system crash.
Recommendation
Apply the patch from the Linux kernel update that moves error handling before handing the packet to the network stack, eliminating the double-free risk.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: xfrm: nat_keepalive: avoid double free on send error nat_keepalive_send() frees the keepalive skb whenever the IPv4 or IPv6 send helper reports an error. That cleanup is only correct before the skb is handed to the output path. Once ip_build_and_send_pkt() or ip6_xmit() takes ownership, the networking stack may already have consumed the skb before returning an error, so freeing it again is unsafe. Handle the pre-handoff failure cases inside nat_keepalive_send_ipv4() and nat_keepalive_send_ipv6(), where the caller still owns the skb, and keep nat_keepalive_send() responsible only for family dispatch and the unsupported-family cleanup path.