{"id":"CVE-2026-98955","state":"PUBLISHED","title":"flow_dissector: avoid u16 truncation of skb->len when computing thoff","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nflow_dissector: avoid u16 truncation of skb->len when computing thoff\n\n__skb_flow_dissect() computes key_control->thoff using:\n\n  key_control->thoff = min_t(u16, nhoff, skb ? skb->len : hlen);\n\nmin_t(u16, ...) casts both arguments to u16 before comparing them.\nWhenever skb->len (or hlen) modulo 65536 is smaller than nhoff, the\ntruncated length wins and thoff is set to a bogus small value, even\nwhen the dissection succeeded. For example, an IPv4/TCP frame with\nskb->len == 65540 and nhoff == 34 gets thoff == 4, so callers such as\nskb_probe_transport_header() point the transport header inside the\nEthernet header.\n\nSuch skbs are not exotic:\n- At the time of commit d0c081b49137 (\"flow_dissector: properly cap\n  thoff field\"), AF_PACKET with PACKET_VNET_HDR could already build GSO\n  skbs larger than 64KB (MTU checks are skipped for GSO, and\n  alloc_skb_with_frags() accepted up to MAX_SKB_FRAGS (17) order-0\n  pages on top of the linear part).\n- BIG TCP now makes skbs larger than 64KB common.\n- The following patch makes tun_get_user() dissect IFF_TAP frames\n  before eth_type_trans() pulls the Ethernet header, so a GSO frame\n  carrying a 65522..65535 byte L3 packet will be dissected with\n  skb->len in [65536, 65549].\n\nCompare as u32 instead. If the resulting offset cannot be represented\nin the u16 key_control->thoff, cap it to U16_MAX and report the\ndissection as failed rather than silently returning a wrong transport\noffset. thoff is still set on failure, as some callers (such as\neth_get_headlen()) use it regardless of the return value.","publishedAt":"2026-10-23T12:19:15.287Z","updatedAt":"2026-10-30T12:40:30.324Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"d0c081b49137cd3200f2023c0875723be66e7ce5","status":"affected","lessThan":"3f6000fdf8a57b9786669869af8a3e050b541bf3","versionType":"git"},{"version":"d0c081b49137cd3200f2023c0875723be66e7ce5","status":"affected","lessThan":"2c2f82b696c5e877f60ea77b7784e906a5e63014","versionType":"git"},{"version":"d0c081b49137cd3200f2023c0875723be66e7ce5","status":"affected","lessThan":"d44e66f5dd99319a32e378b610af7fcf78da985a","versionType":"git"},{"version":"d0c081b49137cd3200f2023c0875723be66e7ce5","status":"affected","lessThan":"d9e08836d06c84abb18470c94b12b131eaccdc7d","versionType":"git"},{"version":"d0c081b49137cd3200f2023c0875723be66e7ce5","status":"affected","lessThan":"50d0cd575cab763f833d6ac6eb6550b23a0b3dae","versionType":"git"},{"version":"d0c081b49137cd3200f2023c0875723be66e7ce5","status":"affected","lessThan":"9993e6a0ac1b5b3101ffba702cacb9f42b9909d8","versionType":"git"},{"version":"d0c081b49137cd3200f2023c0875723be66e7ce5","status":"affected","lessThan":"52efce4755a4b8b82039caa773645ffc80b25362","versionType":"git"},{"version":"d0c081b49137cd3200f2023c0875723be66e7ce5","status":"affected","lessThan":"99bda1ecbd56905f8bd934b9cdccd3bd251192b1","versionType":"git"},{"version":"d35cd5e279881ec36ff8cd82a2d9caebc0cce3fc","status":"affected","versionType":"git"},{"version":"eecfa2eeefe3caef4c8d6b2284f6066c76ab26a1","status":"affected","versionType":"git"},{"version":"80f327285cab6ab8e10c3ea03278add5dd99fb02","status":"affected","versionType":"git"},{"version":"4.4.114","status":"affected","lessThan":"4.5","versionType":"semver"},{"version":"4.9.79","status":"affected","lessThan":"4.10","versionType":"semver"},{"version":"4.14.16","status":"affected","lessThan":"4.15","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/core/flow_dissector.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.15","versionType":"semver"},{"version":"5.10.273","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.224","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.113","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.11","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/core/flow_dissector.c"]}],"references":["https://git.kernel.org/stable/c/3f6000fdf8a57b9786669869af8a3e050b541bf3","https://git.kernel.org/stable/c/2c2f82b696c5e877f60ea77b7784e906a5e63014","https://git.kernel.org/stable/c/d44e66f5dd99319a32e378b610af7fcf78da985a","https://git.kernel.org/stable/c/d9e08836d06c84abb18470c94b12b131eaccdc7d","https://git.kernel.org/stable/c/50d0cd575cab763f833d6ac6eb6550b23a0b3dae","https://git.kernel.org/stable/c/9993e6a0ac1b5b3101ffba702cacb9f42b9909d8","https://git.kernel.org/stable/c/52efce4755a4b8b82039caa773645ffc80b25362","https://git.kernel.org/stable/c/99bda1ecbd56905f8bd934b9cdccd3bd251192b1"],"weaknesses":[],"ingestedAt":"2026-10-30T13:00:06.648Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98955.json","commit":"cb14bf1b43b0c9f05f7f40eae2246263fd430780","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98955","state":"PUBLISHED","datePublished":"2026-10-23T12:19:15.287Z","dateUpdated":"2026-10-30T12:40:30.324Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.382Z"},"containers":{"cna":{"title":"flow_dissector: avoid u16 truncation of skb->len when computing thoff","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nflow_dissector: avoid u16 truncation of skb->len when computing thoff\n\n__skb_flow_dissect() computes key_control->thoff using:\n\n  key_control->thoff = min_t(u16, nhoff, skb ? skb->len : hlen);\n\nmin_t(u16, ...) casts both arguments to u16 before comparing them.\nWhenever skb->len (or hlen) modulo 65536 is smaller than nhoff, the\ntruncated length wins and thoff is set to a bogus small value, even\nwhen the dissection succeeded. For example, an IPv4/TCP frame with\nskb->len == 65540 and nhoff == 34 gets thoff == 4, so callers such as\nskb_probe_transport_header() point the transport header inside the\nEthernet header.\n\nSuch skbs are not exotic:\n- At the time of commit d0c081b49137 (\"flow_dissector: properly cap\n  thoff field\"), AF_PACKET with PACKET_VNET_HDR could already build GSO\n  skbs larger than 64KB (MTU checks are skipped for GSO, and\n  alloc_skb_with_frags() accepted up to MAX_SKB_FRAGS (17) order-0\n  pages on top of the linear part).\n- BIG TCP now makes skbs larger than 64KB common.\n- The following patch makes tun_get_user() dissect IFF_TAP frames\n  before eth_type_trans() pulls the Ethernet header, so a GSO frame\n  carrying a 65522..65535 byte L3 packet will be dissected with\n  skb->len in [65536, 65549].\n\nCompare as u32 instead. If the resulting offset cannot be represented\nin the u16 key_control->thoff, cap it to U16_MAX and report the\ndissection as failed rather than silently returning a wrong transport\noffset. thoff is still set on failure, as some callers (such as\neth_get_headlen()) use it regardless of the return value."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"d0c081b49137cd3200f2023c0875723be66e7ce5","status":"affected","lessThan":"3f6000fdf8a57b9786669869af8a3e050b541bf3","versionType":"git"},{"version":"d0c081b49137cd3200f2023c0875723be66e7ce5","status":"affected","lessThan":"2c2f82b696c5e877f60ea77b7784e906a5e63014","versionType":"git"},{"version":"d0c081b49137cd3200f2023c0875723be66e7ce5","status":"affected","lessThan":"d44e66f5dd99319a32e378b610af7fcf78da985a","versionType":"git"},{"version":"d0c081b49137cd3200f2023c0875723be66e7ce5","status":"affected","lessThan":"d9e08836d06c84abb18470c94b12b131eaccdc7d","versionType":"git"},{"version":"d0c081b49137cd3200f2023c0875723be66e7ce5","status":"affected","lessThan":"50d0cd575cab763f833d6ac6eb6550b23a0b3dae","versionType":"git"},{"version":"d0c081b49137cd3200f2023c0875723be66e7ce5","status":"affected","lessThan":"9993e6a0ac1b5b3101ffba702cacb9f42b9909d8","versionType":"git"},{"version":"d0c081b49137cd3200f2023c0875723be66e7ce5","status":"affected","lessThan":"52efce4755a4b8b82039caa773645ffc80b25362","versionType":"git"},{"version":"d0c081b49137cd3200f2023c0875723be66e7ce5","status":"affected","lessThan":"99bda1ecbd56905f8bd934b9cdccd3bd251192b1","versionType":"git"},{"version":"d35cd5e279881ec36ff8cd82a2d9caebc0cce3fc","status":"affected","versionType":"git"},{"version":"eecfa2eeefe3caef4c8d6b2284f6066c76ab26a1","status":"affected","versionType":"git"},{"version":"80f327285cab6ab8e10c3ea03278add5dd99fb02","status":"affected","versionType":"git"},{"version":"4.4.114","status":"affected","lessThan":"4.5","versionType":"semver"},{"version":"4.9.79","status":"affected","lessThan":"4.10","versionType":"semver"},{"version":"4.14.16","status":"affected","lessThan":"4.15","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/core/flow_dissector.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.15","versionType":"semver"},{"version":"5.10.273","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.224","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.113","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.11","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/core/flow_dissector.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/3f6000fdf8a57b9786669869af8a3e050b541bf3"},{"url":"https://git.kernel.org/stable/c/2c2f82b696c5e877f60ea77b7784e906a5e63014"},{"url":"https://git.kernel.org/stable/c/d44e66f5dd99319a32e378b610af7fcf78da985a"},{"url":"https://git.kernel.org/stable/c/d9e08836d06c84abb18470c94b12b131eaccdc7d"},{"url":"https://git.kernel.org/stable/c/50d0cd575cab763f833d6ac6eb6550b23a0b3dae"},{"url":"https://git.kernel.org/stable/c/9993e6a0ac1b5b3101ffba702cacb9f42b9909d8"},{"url":"https://git.kernel.org/stable/c/52efce4755a4b8b82039caa773645ffc80b25362"},{"url":"https://git.kernel.org/stable/c/99bda1ecbd56905f8bd934b9cdccd3bd251192b1"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:40:30.324Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"5.10.273"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"5.15.224"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"6.12.113"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"6.18.57"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"7.2.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","ve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