High [CVE-2026-72137] avoid double free on send error
This high-severity Red Hat Linux advisory covers CVE-2026-72137 affecting Red Hat Enterprise Linux 10, Red Hat package: kernel.
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Summary
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. A flaw was found in the `xfrm` subsystem of the Linux kernel, specifically within the `nat_keepalive` component.
This vulnerability occurs when the `nat_keepalive_send()` function attempts to free a network packet buffer (skb) that may have already been freed by the networking stack. This double free can lead to memory corruption, potentially resulting in a denial of service or other unpredictable system behavior.
This issue does not affect the versions of the kernel as shipped with Red Hat Enterprise Linux 6, 7, 8, and 9, as the vulnerable xfrm NAT keepalive code was introduced in Linux 6.11.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 22 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 22 days ago·verify at source
Mitigation checklist
- Update to the latest stable kernel version. Fixes are available for versions 6.12.101, 6.18.40, 7.1.5, and 7.2-rc4.
Official advisory · high-confidence parse· fetched 22 days ago·verify at source
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