{"id":"CVE-2026-72250","summary":"netfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag\n\nnf_ct_frag6_reasm() slides the packet head forward to drop the IPv6\nfragment header and then unconditionally advances skb-\u003emac_header:\n\n\tskb-\u003emac_header += sizeof(struct frag_hdr);\n\nOn the NF_INET_LOCAL_OUT defrag path the skb has no link-layer header\nyet, so skb-\u003emac_header is still the \"not set\" sentinel (u16)~0U. Adding\nsizeof(struct frag_hdr) wraps it to a small value (0xffff + 8 == 7),\nafter which skb_mac_header_was_set() wrongly reports a MAC header is\npresent and skb_mac_header() points into the headroom.\n\nThe reassembler has done this unconditional add since it was introduced;\nit was harmless while mac_header was a bare pointer, but wrong once\nmac_header became a u16 offset whose unset state is the ~0U sentinel\ntested by skb_mac_header_was_set(). The sibling net/ipv6/reassembly.c\ndoes the same relocation and does guard the adjustment; mirror the\nguard here.","modified":"2026-08-18T03:56:22.813952066Z","published":"2026-08-15T05:54:39.134Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72250.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/00bdce2fda7e430d24cfbc96764a1b96deb31f82"},{"type":"WEB","url":"https://git.kernel.org/stable/c/2a95ec21824a8ad81ad660b12231456fc0ac9830"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3b08fed5b7e0d5e3a25d73ef3ba09cd33ade16c9"},{"type":"WEB","url":"https://git.kernel.org/stable/c/53ef70a315420ed31581d38343684b3bf9a3c76d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6e8cd710ca35c576f5f2e5a396047c9ac61f75e5"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a58230f3a7c4f6c3261786bc1efb72c42e68cd25"},{"type":"WEB","url":"https://git.kernel.org/stable/c/bbcdef2061b170af45702ce6b359c02c12acfc94"},{"type":"WEB","url":"https://git.kernel.org/stable/c/cd0d7bbc027b4d3329712cdcdeb4e5567ffd0d58"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72250.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72250"},{"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":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1"},{"fixed":"6e8cd710ca35c576f5f2e5a396047c9ac61f75e5"},{"fixed":"2a95ec21824a8ad81ad660b12231456fc0ac9830"},{"fixed":"bbcdef2061b170af45702ce6b359c02c12acfc94"},{"fixed":"cd0d7bbc027b4d3329712cdcdeb4e5567ffd0d58"},{"fixed":"53ef70a315420ed31581d38343684b3bf9a3c76d"},{"fixed":"a58230f3a7c4f6c3261786bc1efb72c42e68cd25"},{"fixed":"00bdce2fda7e430d24cfbc96764a1b96deb31f82"},{"fixed":"3b08fed5b7e0d5e3a25d73ef3ba09cd33ade16c9"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72250.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.6.15"},{"fixed":"5.10.261"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.212"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.178"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.145"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.97"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.40"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.5"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72250.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}