{"id":"CVE-2026-90078","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_skbmod: fix length calculations and avoid invalid header warnings\n\nsyzbot reported a warning in skb_network_header_len() triggered\nby tcf_skbmod_act():\n\n…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_skbmod: fix length calculations and avoid invalid header warnings\n\nsyzbot reported a warning in skb_network_header_len() triggered\nby tcf_skbmod_act():\n\n…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 56af5e749f20c3a540310c207dcc373f4f09156e < 985a37781ade19061400100c2ba0f43979dd4d63","Linux >= 56af5e749f20c3a540310c207dcc373f4f09156e < d896843d8d925f0adbba319020595cfb1a7bcd57","Linux >= 56af5e749f20c3a540310c207dcc373f4f09156e < 0675cff3c2924eb9b80d9dd250cf56a1140af157","Linux >= 56af5e749f20c3a540310c207dcc373f4f09156e < e8a2027b7e686784a69b2dfcee841d779919f313","Linux >= 56af5e749f20c3a540310c207dcc373f4f09156e < 1719865b20b22c88d2a55e922eff5ca31b0841f6","Linux >= 56af5e749f20c3a540310c207dcc373f4f09156e < 62126464f3a6159c0a3dd89e196ba65bfeb0afc6","Linux >= 56af5e749f20c3a540310c207dcc373f4f09156e < 81d0d1e64f30d9989c829c0953cd6e6c68d9c5fb","Linux 5.15"],"published":"2026-09-17","updated":"2026-09-17","sourceUpdated":"2026-09-17T17:16:57.057","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-90078","references":[{"url":"https://git.kernel.org/stable/c/0675cff3c2924eb9b80d9dd250cf56a1140af157","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/1719865b20b22c88d2a55e922eff5ca31b0841f6","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/62126464f3a6159c0a3dd89e196ba65bfeb0afc6","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/81d0d1e64f30d9989c829c0953cd6e6c68d9c5fb","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/985a37781ade19061400100c2ba0f43979dd4d63","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/d896843d8d925f0adbba319020595cfb1a7bcd57","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/e8a2027b7e686784a69b2dfcee841d779919f313","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd","cve.org"],"ingestedAt":"2026-09-17T16:21:47.896Z","epss":0.00206,"epssPercentile":0.10943,"slug":"CVE-2026-90078","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_skbmod: fix length calculations and avoid invalid header warnings\n\nsyzbot reported a warning in skb_network_header_len() triggered\nby tcf_skbmod_act():\n\n  !skb_transport_header_was_set(skb)\n  WARNING: CPU: 0 PID: 14949 at include/linux/skbuff.h:3243 skb_network_header_len include/linux/skbuff.h:3243 [inline]\n  WARNING: CPU: 0 PID: 14949 at net/sched/act_skbmod.c:55 tcf_skbmod_act+0xfe8/0x1810 net/sched/act_skbmod.c:55\n\nThere are a few issues in tcf_skbmod_act():\n\n1. Calling skb_network_header_len() assumes skb->transport_header is set,\n   which is not guaranteed when tcf_skbmod_act() runs at TC ingress.\n2. Unconditionally calling skb_mac_header_len() at the beginning of\n   tcf_skbmod_act() triggers a warning on L3 devices (e.g. TUN) where the\n   MAC header is unset, evaluating to an underflowed garbage length.\n3. On TC ingress, skb->data points to the network header. Adding the MAC\n   header length to the IP header length causes skb_ensure_writable() to\n   request more bytes than the actual IP packet length, dropping valid\n   short packets (e.g. 28-byte UDP/IPv4 packets).\n\nFix these by:\n- Using skb_network_offset(skb) + sizeof(struct iphdr/ipv6hdr) for\n  SKBMOD_F_ECN so that the required length is correctly calculated on\n  both ingress (offset == 0) and egress (offset == mac_len).\n- Setting max_edit_len to ETH_HLEN for Ethernet header modifications\n  after validating ARPHRD_ETHER.\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":[]}