CVE-2026-80792

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CVE-2026-80792

Summary: ipv6: fix use-after-free in ip6_finish_output2()

Details: In the Linux kernel, the following vulnerability has been resolved: ipv6: fix use-after-free in ip6_finish_output2() ip6_finish_output2() caches a pointer to the IPv6 destination address (daddr) before invoking lwtunnel_xmit(). The LWT-BPF transmit path or other encapsulation operations within lwtunnel_xmit() can reallocate the skb head, freeing the memory that daddr points to. When lwtunnel_xmit() returns LWTUNNEL_XMIT_CONTINUE, the function continues to use the stale daddr pointer to compute the nexthop and to look up or create the neighbour entry. This results in a use-after-free read, which can leak sensitive kernel data, pollute the neighbour table with arbitrary values, misdirect traffic, or crash the system. Fix this by re-fetching the IPv6 header and the destination address pointer after lwtunnel_xmit() returns LWTUNNEL_XMIT_CONTINUE, ensuring that the subsequent nexthop computation and neighbour lookup operate on valid memory.

References: https://git.kernel.org/stable/c/087ee0d914aaae929f1660c9ca878e367655ba1a, https://git.kernel.org/stable/c/3c770ac4e6f07af7c7b40c474a3efc61ffed7862, https://git.kernel.org/stable/c/3dc98e5fe82d069dd29b124ffbdb679331dfea43, https://git.kernel.org/stable/c/73a187384a8c8b983c7fea046d716b6752a1e7a3, https://git.kernel.org/stable/c/75e0a544ebe9af663ef53ca21e9e9185c51fb54a, https://git.kernel.org/stable/c/99219c82804f266189388e8bf1cf5135d10d5515, https://git.kernel.org/stable/c/c95f01b78266828a57060d754fcbfc92123a98ed, https://git.kernel.org/stable/c/d0d48d999b0eee6bb176ef4e39d9be868fa80f7e, https://git.kernel.org/stable/c/d960881b9312e781a3429aabceb223ce6b7c882f, https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80792.json, https://nvd.nist.gov/vuln/detail/CVE-2026-80792, https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git