{"id":"CVE-2026-80976","summary":"seg6: reset IP6CB after IPv6 decapsulation","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nseg6: reset IP6CB after IPv6 decapsulation\n\ndecap_and_validate() pulls the outer SRv6 headers and makes the inner\npacket the skb network header. The IPv6 control block still contains\nvalues collected while parsing the outer packet, including nhoff and\nextension-header flags.\n\nEnd.DX6 and End.DT6 route the inner IPv6 packet directly to the IPv6\ninput path. An unprivileged user can reach End.DT6 from a user and net\nnamespace by installing a local SID and injecting an outer packet with\nHop-by-Hop and Destination Options headers followed by an SRH and a\nminimal inner IPv6 packet.\n\nThe outer extension headers leave a large nhoff in IP6CB. After\ndecapsulation, ip6_protocol_deliver_rcu() uses that stale offset on the\ninner packet and reads beyond the skb head. KASAN reports:\n\n  BUG: KASAN: slab-out-of-bounds in ip6_protocol_deliver_rcu\n  ip6_protocol_deliver_rcu+0x1118/0x1450\n  ip6_input_finish+0x11b/0x240\n  seg6_local_input_core+0xed/0x2e0\n  lwtunnel_input+0x1e9/0x4e0\n  ipv6_rthdr_rcv+0x525f/0x6c50\n  ip6_protocol_deliver_rcu+0xcb7/0x1450\n\nBefore clearing IP6CB for an inner IPv6 packet, save its incoming\ninterface index and L3 slave state. Restore both after the clear and set\nnhoff to the inner IPv6 base-header nexthdr field.\n\nUse IP6CB(skb)-\u003eiif rather than skb-\u003eskb_iif because VRF processing can\nreplace skb_iif with the L3 master while IP6CB keeps the receiving\ninterface. Preserve IP6SKB_L3SLAVE for the same reason.","modified":"2026-09-13T03:47:03.082462454Z","published":"2026-09-11T19:42:38.215Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80976.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/2b154e96fcb3f01fd42765c64e0a56820fbc16eb"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c73fb911e02b9a766c950bc9707f3e3a96ffd702"},{"type":"WEB","url":"https://git.kernel.org/stable/c/cfa186a0857a0f831dfca67b16bbc40ecfdf3280"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f967455fb2a5a2079b9eb5823e9ccf359174bf9f"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80976.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-80976"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"d7a669dd2f8ba07a17423f4ad586dfc0379882f7"},{"fixed":"2b154e96fcb3f01fd42765c64e0a56820fbc16eb"},{"fixed":"cfa186a0857a0f831dfca67b16bbc40ecfdf3280"},{"fixed":"c73fb911e02b9a766c950bc9707f3e3a96ffd702"},{"fixed":"f967455fb2a5a2079b9eb5823e9ccf359174bf9f"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80976.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.14.0"},{"fixed":"6.12.109"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.50"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.4"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80976.json"}}],"schema_version":"1.9.0"}