{"id":"CVE-2026-98955","title":"flow_dissector: avoid u16 truncation of skb->len when computing thoff","summary":"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,…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= d0c081b49137cd3200f2023c0875723be66e7ce5 < d9e08836d06c84abb18470c94b12b131eaccdc7d","Linux >= d0c081b49137cd3200f2023c0875723be66e7ce5 < 50d0cd575cab763f833d6ac6eb6550b23a0b3dae","Linux >= d0c081b49137cd3200f2023c0875723be66e7ce5 < 9993e6a0ac1b5b3101ffba702cacb9f42b9909d8","Linux >= d0c081b49137cd3200f2023c0875723be66e7ce5 < 52efce4755a4b8b82039caa773645ffc80b25362","Linux >= d0c081b49137cd3200f2023c0875723be66e7ce5 < 99bda1ecbd56905f8bd934b9cdccd3bd251192b1","Linux d35cd5e279881ec36ff8cd82a2d9caebc0cce3fc","Linux eecfa2eeefe3caef4c8d6b2284f6066c76ab26a1","Linux 80f327285cab6ab8e10c3ea03278add5dd99fb02","Linux >= 4.4.114 < 4.5","Linux >= 4.9.79 < 4.10","Linux >= 4.14.16 < 4.15","Linux 4.15"],"published":"2026-10-23","updated":"2026-10-23","sourceUpdated":"2026-10-23T12:19:15.287Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98955","references":[{"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"}],"tags":["cve.org"],"ingestedAt":"2026-10-23T13:24:55.557Z","slug":"CVE-2026-98955","body":"## Overview\n\nIn 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.\n\n## Affected\n\n- `Linux >= d0c081b49137cd3200f2023c0875723be66e7ce5 < d9e08836d06c84abb18470c94b12b131eaccdc7d`\n- `Linux >= d0c081b49137cd3200f2023c0875723be66e7ce5 < 50d0cd575cab763f833d6ac6eb6550b23a0b3dae`\n- `Linux >= d0c081b49137cd3200f2023c0875723be66e7ce5 < 9993e6a0ac1b5b3101ffba702cacb9f42b9909d8`\n- `Linux >= d0c081b49137cd3200f2023c0875723be66e7ce5 < 52efce4755a4b8b82039caa773645ffc80b25362`\n- `Linux >= d0c081b49137cd3200f2023c0875723be66e7ce5 < 99bda1ecbd56905f8bd934b9cdccd3bd251192b1`\n- `Linux d35cd5e279881ec36ff8cd82a2d9caebc0cce3fc`\n- `Linux eecfa2eeefe3caef4c8d6b2284f6066c76ab26a1`\n- `Linux 80f327285cab6ab8e10c3ea03278add5dd99fb02`\n- `Linux >= 4.4.114 < 4.5`\n- `Linux >= 4.9.79 < 4.10`\n- `Linux >= 4.14.16 < 4.15`\n- `Linux 4.15`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}