{"id":"CVE-2026-90078","revision":"dfff20be234a41bb988d5f906fabf02c","records":[{"revision":"dfff20be234a41bb988d5f906fabf02c","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-90078","aliases":[],"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.","state":0,"publishedAt":"2026-09-17T16:05:56.878+00:00","modifiedAt":"2026-10-19T08:57:34.924+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"net/sched/act_skbmod.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"56af5e749f20c3a540310c207dcc373f4f09156e\",\n                            \"lessThan\": \"985a37781ade19061400100c2ba0f43979dd4d63\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"56af5e749f20c3a540310c207dcc373f4f09156e\",\n                            \"lessThan\": \"d896843d8d925f0adbba319020595cfb1a7bcd57\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"56af5e749f20c3a540310c207dcc373f4f09156e\",\n                            \"lessThan\": \"0675cff3c2924eb9b80d9dd250cf56a1140af157\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"56af5e749f20c3a540310c207dcc373f4f09156e\",\n                            \"lessThan\": \"e8a2027b7e686784a69b2dfcee841d779919f313\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"56af5e749f20c3a540310c207dcc373f4f09156e\",\n                            \"lessThan\": \"1719865b20b22c88d2a55e922eff5ca31b0841f6\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"56af5e749f20c3a540310c207dcc373f4f09156e\",\n                            \"lessThan\": \"62126464f3a6159c0a3dd89e196ba65bfeb0afc6\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"56af5e749f20c3a540310c207dcc373f4f09156e\",\n                            \"lessThan\": \"81d0d1e64f30d9989c829c0953cd6e6c68d9c5fb\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"net/sched/act_skbmod.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"5.15\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"5.15\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.221\",\n                            \"lessThanOrEqual\": \"5.15.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.188\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.157\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.110\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.52\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2.6\",\n                            \"lessThanOrEqual\": \"7.2.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.3\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[],"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"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-90078","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-90078","identifiers":["CVE-2026-90078"]},"retained":false,"historicalAffected":[]}],"coverage":[]}