{"id":"CVE-2026-98371","summary":"xfrm: iptfs: fix runt reassembly panic from short inner tot_len","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: iptfs: fix runt reassembly panic from short inner tot_len\n\nWhen the start of an inner packet is split across two outer packets\nsuch that fewer than 4 bytes land at the end of the first one,\n__input_process_payload() saves those bytes as a runt and skips the\niplen/iphlen validation performed for in-place packets. When the\ncontinuation packet arrives, iptfs_reassem_cont() only requires the\ndeclared inner length to be \u003e= sizeof(ra_runt) (6) before allocating\nthe reassembly skb with that attacker-controlled length.\n\nHowever, __iptfs_iphlen() always returns the fixed minimum IP header\nsize (20 for IPv4, 40 for IPv6), so for an inner IPv4 tot_len in\n[6, 19] the header-completion copy writes past the declared packet\nlength, and the subsequent \"ipremain -= copylen\" underflows to ~4GB,\nleaving the payload copy length bounded only by blkoff (up to 64KB).\nAt runtime the skb_put() tailroom check turns this into\nskb_over_panic(), i.e. an unprivileged kernel panic (DoS), reachable\nlocally via userns+netns IPTFS SAs and remotely against IPTFS VPN\ngateways when the decrypted outer skb is linear (e.g. AF_PACKET taps,\ntun/tap delivery).\n\nAlign the runt path with the normal path by requiring the declared\ninner length to cover at least the IP header size. This also subsumes\nthe previous \u003e= sizeof(ra_runt) check, since the minimum IP header\nis always larger than the runt buffer.\n\nThis issue was found by the autokbug dynamic kernel fuzzer at\nTencent Yunding Lab.","modified":"2026-10-08T02:52:58.340559668Z","published":"2026-10-06T08:46:55.753Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98371.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/5b8afb56ccb7c014b0f1ac40341708b200443c2d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a7018ee0ea8622ed59edc064be4e0f2c26464f53"},{"type":"WEB","url":"https://git.kernel.org/stable/c/dc33262be1fe43d0eb0b84fb58c6ed42e2f64a8c"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98371.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98371"},{"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":"07569476544681816335099929ff3494dfbf6b05"},{"fixed":"a7018ee0ea8622ed59edc064be4e0f2c26464f53"},{"fixed":"5b8afb56ccb7c014b0f1ac40341708b200443c2d"},{"fixed":"dc33262be1fe43d0eb0b84fb58c6ed42e2f64a8c"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98371.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.14.0"},{"fixed":"6.18.54"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.8"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98371.json"}}],"schema_version":"1.9.0"}