{"id":"CVE-2026-90078","state":"PUBLISHED","title":"net/sched: act_skbmod: fix length calculations and avoid invalid header warnings","description":"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  !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.","publishedAt":"2026-09-17T16:05:56.878Z","updatedAt":"2026-10-19T08:57:34.924Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"56af5e749f20c3a540310c207dcc373f4f09156e","status":"affected","lessThan":"985a37781ade19061400100c2ba0f43979dd4d63","versionType":"git"},{"version":"56af5e749f20c3a540310c207dcc373f4f09156e","status":"affected","lessThan":"d896843d8d925f0adbba319020595cfb1a7bcd57","versionType":"git"},{"version":"56af5e749f20c3a540310c207dcc373f4f09156e","status":"affected","lessThan":"0675cff3c2924eb9b80d9dd250cf56a1140af157","versionType":"git"},{"version":"56af5e749f20c3a540310c207dcc373f4f09156e","status":"affected","lessThan":"e8a2027b7e686784a69b2dfcee841d779919f313","versionType":"git"},{"version":"56af5e749f20c3a540310c207dcc373f4f09156e","status":"affected","lessThan":"1719865b20b22c88d2a55e922eff5ca31b0841f6","versionType":"git"},{"version":"56af5e749f20c3a540310c207dcc373f4f09156e","status":"affected","lessThan":"62126464f3a6159c0a3dd89e196ba65bfeb0afc6","versionType":"git"},{"version":"56af5e749f20c3a540310c207dcc373f4f09156e","status":"affected","lessThan":"81d0d1e64f30d9989c829c0953cd6e6c68d9c5fb","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/act_skbmod.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.15","versionType":"semver"},{"version":"5.15.221","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.188","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.157","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.110","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.52","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.6","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/sched/act_skbmod.c"]}],"references":["https://git.kernel.org/stable/c/985a37781ade19061400100c2ba0f43979dd4d63","https://git.kernel.org/stable/c/d896843d8d925f0adbba319020595cfb1a7bcd57","https://git.kernel.org/stable/c/0675cff3c2924eb9b80d9dd250cf56a1140af157","https://git.kernel.org/stable/c/e8a2027b7e686784a69b2dfcee841d779919f313","https://git.kernel.org/stable/c/1719865b20b22c88d2a55e922eff5ca31b0841f6","https://git.kernel.org/stable/c/62126464f3a6159c0a3dd89e196ba65bfeb0afc6","https://git.kernel.org/stable/c/81d0d1e64f30d9989c829c0953cd6e6c68d9c5fb"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:34.582Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/90xxx/CVE-2026-90078.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-90078","state":"PUBLISHED","datePublished":"2026-09-17T16:05:56.878Z","dateUpdated":"2026-10-19T08:57:34.924Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-11T19:38:34.785Z"},"containers":{"cna":{"title":"net/sched: act_skbmod: fix length calculations and avoid invalid header warnings","descriptions":[{"lang":"en","value":"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  !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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"56af5e749f20c3a540310c207dcc373f4f09156e","status":"affected","lessThan":"985a37781ade19061400100c2ba0f43979dd4d63","versionType":"git"},{"version":"56af5e749f20c3a540310c207dcc373f4f09156e","status":"affected","lessThan":"d896843d8d925f0adbba319020595cfb1a7bcd57","versionType":"git"},{"version":"56af5e749f20c3a540310c207dcc373f4f09156e","status":"affected","lessThan":"0675cff3c2924eb9b80d9dd250cf56a1140af157","versionType":"git"},{"version":"56af5e749f20c3a540310c207dcc373f4f09156e","status":"affected","lessThan":"e8a2027b7e686784a69b2dfcee841d779919f313","versionType":"git"},{"version":"56af5e749f20c3a540310c207dcc373f4f09156e","status":"affected","lessThan":"1719865b20b22c88d2a55e922eff5ca31b0841f6","versionType":"git"},{"version":"56af5e749f20c3a540310c207dcc373f4f09156e","status":"affected","lessThan":"62126464f3a6159c0a3dd89e196ba65bfeb0afc6","versionType":"git"},{"version":"56af5e749f20c3a540310c207dcc373f4f09156e","status":"affected","lessThan":"81d0d1e64f30d9989c829c0953cd6e6c68d9c5fb","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/act_skbmod.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.15","versionType":"semver"},{"version":"5.15.221","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.188","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.157","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.110","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.52","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.6","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/sched/act_skbmod.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/985a37781ade19061400100c2ba0f43979dd4d63"},{"url":"https://git.kernel.org/stable/c/d896843d8d925f0adbba319020595cfb1a7bcd57"},{"url":"https://git.kernel.org/stable/c/0675cff3c2924eb9b80d9dd250cf56a1140af157"},{"url":"https://git.kernel.org/stable/c/e8a2027b7e686784a69b2dfcee841d779919f313"},{"url":"https://git.kernel.org/stable/c/1719865b20b22c88d2a55e922eff5ca31b0841f6"},{"url":"https://git.kernel.org/stable/c/62126464f3a6159c0a3dd89e196ba65bfeb0afc6"},{"url":"https://git.kernel.org/stable/c/81d0d1e64f30d9989c829c0953cd6e6c68d9c5fb"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T08:57:34.924Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"5.15.221"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.1.188"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.6.157"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.12.110"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.18.52"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"7.2.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}