{"id":"CVE-2026-99033","state":"PUBLISHED","title":"net/packet: guard the ll header push in packet_rcv_spkt()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/packet: guard the ll header push in packet_rcv_spkt()\n\npacket_rcv_spkt() restores the link layer header with\n\n\tskb_push(skb, skb->data - skb_mac_header(skb));\n\nThat subtraction is only meaningful when the device actually has a link\nlayer header.  packet_rcv() and tpacket_rcv() both wrap it in\ndev_has_header(), which is also the predicate the block comment at the\ntop of the file states the restore in terms of; packet_rcv_spkt() does\nnot.  commit d549699048b4 (\"net/packet: fix packet receive on L3\ndevices without visible hard header\") introduced the helper and changed\nthe two call sites, and this one stayed behind.\n\nA device without a visible ll header can leave skb->mac_header at the\n0xFFFF sentinel that __alloc_skb() initialises it to.  A CAN skb does:\ninit_can_skb() sets pkt_type and ip_summed but does not reset the\nheaders, and commit 9f10374bb024 (\"can: remove private CAN skb\nheadroom infrastructure\") dropped the skb_reset_*_header() calls that\nused to be there.  skb_mac_header() is then 0xFFFF, the length becomes\na large negative number and skb_push() reports it through\nskb_under_panic() -- from softirq context, so it is a full system panic\neven with panic_on_oops=0:\n\n  skbuff: skb_under_panic: text:ffffffff8bd21bc1 len:-65455 put:-65471 head:... data:... tail:0x50 end:0x180 dev:can0\n  kernel BUG at net/core/skbuff.c:214!\n  RIP: 0010:skb_panic+0x50/0x60\n  Call Trace:\n   <IRQ>\n   skb_push+0x38/0x40\n   packet_rcv_spkt+0xe1/0x170\n   __netif_receive_skb_core.constprop.0+0x7e8/0xd30\n   ...\n  Kernel panic - not syncing: Fatal exception in interrupt\n\nThe socket type is reachable: packet_create() accepts SOCK_PACKET\nalongside SOCK_RAW and SOCK_DGRAM behind the same CAP_NET_RAW check,\nand neither the socket length nor a capability check keeps it away\nfrom a CAN interface.\n\nThe missing skb_reset_*_header() calls in init_can_skb() are a\nregression in their own right and are being fixed separately, but a\npacket socket should not turn a link layer that did not initialise its\nmac header into a kernel panic.  Guard the push the way the other two\nreceive paths do.\n\nTested on v7.3-rc5 under QEMU with a slcan device on a pty, which is\nthe driver RX path: vcan does not reproduce it, because can_send()\nresets the headers on the way out.  One SOCK_PACKET socket bound to\ncan0 and one frame written into the line discipline panics an\nunpatched kernel with the trace above; the same image with this patch\nprints no panic and powers off normally.  Both kernels are this tree,\ndefconfig plus CONFIG_CAN_SLCAN=y, differing only in this hunk.","publishedAt":"2026-10-23T12:21:37.662Z","updatedAt":"2026-10-30T12:41:06.206Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"d549699048b4b5c22dd710455bcdb76966e55aa3","status":"affected","lessThan":"48aa1155fa8d83362fc33d02d527a3c3fe40ce1c","versionType":"git"},{"version":"d549699048b4b5c22dd710455bcdb76966e55aa3","status":"affected","lessThan":"7f84ed94ccfe36091234a2891b88356dc06e6d66","versionType":"git"},{"version":"d549699048b4b5c22dd710455bcdb76966e55aa3","status":"affected","lessThan":"b880df0e487caa85c3c7ffda37dcd05334b1aa80","versionType":"git"},{"version":"d549699048b4b5c22dd710455bcdb76966e55aa3","status":"affected","lessThan":"d8a24b9e1774a93943caf68d48c5e17be432220b","versionType":"git"},{"version":"d549699048b4b5c22dd710455bcdb76966e55aa3","status":"affected","lessThan":"31c7b15b3716e8d0dad58d2c3cdf321dfd06f4be","versionType":"git"},{"version":"d549699048b4b5c22dd710455bcdb76966e55aa3","status":"affected","lessThan":"3efe0e0944157fdd2072b4dc7eb0491a317ed272","versionType":"git"},{"version":"d549699048b4b5c22dd710455bcdb76966e55aa3","status":"affected","lessThan":"00fbf71e74115f7628fc0880b855434b1e70c40c","versionType":"git"},{"version":"d549699048b4b5c22dd710455bcdb76966e55aa3","status":"affected","lessThan":"28bc1ef699610ee09ce3d46a00552f5a0a0144bd","versionType":"git"},{"version":"dadddde259a19105ee69e788835f4d4552767aa9","status":"affected","versionType":"git"},{"version":"5.9.13","status":"affected","lessThan":"5.10","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/packet/af_packet.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.10","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.10","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/packet/af_packet.c"]}],"references":["https://git.kernel.org/stable/c/48aa1155fa8d83362fc33d02d527a3c3fe40ce1c","https://git.kernel.org/stable/c/7f84ed94ccfe36091234a2891b88356dc06e6d66","https://git.kernel.org/stable/c/b880df0e487caa85c3c7ffda37dcd05334b1aa80","https://git.kernel.org/stable/c/d8a24b9e1774a93943caf68d48c5e17be432220b","https://git.kernel.org/stable/c/31c7b15b3716e8d0dad58d2c3cdf321dfd06f4be","https://git.kernel.org/stable/c/3efe0e0944157fdd2072b4dc7eb0491a317ed272","https://git.kernel.org/stable/c/00fbf71e74115f7628fc0880b855434b1e70c40c","https://git.kernel.org/stable/c/28bc1ef699610ee09ce3d46a00552f5a0a0144bd"],"weaknesses":[],"ingestedAt":"2026-10-30T13:00:06.648Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/99xxx/CVE-2026-99033.json","commit":"cb14bf1b43b0c9f05f7f40eae2246263fd430780","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-99033","state":"PUBLISHED","datePublished":"2026-10-23T12:21:37.662Z","dateUpdated":"2026-10-30T12:41:06.206Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.387Z"},"containers":{"cna":{"title":"net/packet: guard the ll header push in packet_rcv_spkt()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/packet: guard the ll header push in packet_rcv_spkt()\n\npacket_rcv_spkt() restores the link layer header with\n\n\tskb_push(skb, skb->data - skb_mac_header(skb));\n\nThat subtraction is only meaningful when the device actually has a link\nlayer header.  packet_rcv() and tpacket_rcv() both wrap it in\ndev_has_header(), which is also the predicate the block comment at the\ntop of the file states the restore in terms of; packet_rcv_spkt() does\nnot.  commit d549699048b4 (\"net/packet: fix packet receive on L3\ndevices without visible hard header\") introduced the helper and changed\nthe two call sites, and this one stayed behind.\n\nA device without a visible ll header can leave skb->mac_header at the\n0xFFFF sentinel that __alloc_skb() initialises it to.  A CAN skb does:\ninit_can_skb() sets pkt_type and ip_summed but does not reset the\nheaders, and commit 9f10374bb024 (\"can: remove private CAN skb\nheadroom infrastructure\") dropped the skb_reset_*_header() calls that\nused to be there.  skb_mac_header() is then 0xFFFF, the length becomes\na large negative number and skb_push() reports it through\nskb_under_panic() -- from softirq context, so it is a full system panic\neven with panic_on_oops=0:\n\n  skbuff: skb_under_panic: text:ffffffff8bd21bc1 len:-65455 put:-65471 head:... data:... tail:0x50 end:0x180 dev:can0\n  kernel BUG at net/core/skbuff.c:214!\n  RIP: 0010:skb_panic+0x50/0x60\n  Call Trace:\n   <IRQ>\n   skb_push+0x38/0x40\n   packet_rcv_spkt+0xe1/0x170\n   __netif_receive_skb_core.constprop.0+0x7e8/0xd30\n   ...\n  Kernel panic - not syncing: Fatal exception in interrupt\n\nThe socket type is reachable: packet_create() accepts SOCK_PACKET\nalongside SOCK_RAW and SOCK_DGRAM behind the same CAP_NET_RAW check,\nand neither the socket length nor a capability check keeps it away\nfrom a CAN interface.\n\nThe missing skb_reset_*_header() calls in init_can_skb() are a\nregression in their own right and are being fixed separately, but a\npacket socket should not turn a link layer that did not initialise its\nmac header into a kernel panic.  Guard the push the way the other two\nreceive paths do.\n\nTested on v7.3-rc5 under QEMU with a slcan device on a pty, which is\nthe driver RX path: vcan does not reproduce it, because can_send()\nresets the headers on the way out.  One SOCK_PACKET socket bound to\ncan0 and one frame written into the line discipline panics an\nunpatched kernel with the trace above; the same image with this patch\nprints no panic and powers off normally.  Both kernels are this tree,\ndefconfig plus CONFIG_CAN_SLCAN=y, differing only in this hunk."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"d549699048b4b5c22dd710455bcdb76966e55aa3","status":"affected","lessThan":"48aa1155fa8d83362fc33d02d527a3c3fe40ce1c","versionType":"git"},{"version":"d549699048b4b5c22dd710455bcdb76966e55aa3","status":"affected","lessThan":"7f84ed94ccfe36091234a2891b88356dc06e6d66","versionType":"git"},{"version":"d549699048b4b5c22dd710455bcdb76966e55aa3","status":"affected","lessThan":"b880df0e487caa85c3c7ffda37dcd05334b1aa80","versionType":"git"},{"version":"d549699048b4b5c22dd710455bcdb76966e55aa3","status":"affected","lessThan":"d8a24b9e1774a93943caf68d48c5e17be432220b","versionType":"git"},{"version":"d549699048b4b5c22dd710455bcdb76966e55aa3","status":"affected","lessThan":"31c7b15b3716e8d0dad58d2c3cdf321dfd06f4be","versionType":"git"},{"version":"d549699048b4b5c22dd710455bcdb76966e55aa3","status":"affected","lessThan":"3efe0e0944157fdd2072b4dc7eb0491a317ed272","versionType":"git"},{"version":"d549699048b4b5c22dd710455bcdb76966e55aa3","status":"affected","lessThan":"00fbf71e74115f7628fc0880b855434b1e70c40c","versionType":"git"},{"version":"d549699048b4b5c22dd710455bcdb76966e55aa3","status":"affected","lessThan":"28bc1ef699610ee09ce3d46a00552f5a0a0144bd","versionType":"git"},{"version":"dadddde259a19105ee69e788835f4d4552767aa9","status":"affected","versionType":"git"},{"version":"5.9.13","status":"affected","lessThan":"5.10","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/packet/af_packet.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.10","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.10","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/packet/af_packet.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/48aa1155fa8d83362fc33d02d527a3c3fe40ce1c"},{"url":"https://git.kernel.org/stable/c/7f84ed94ccfe36091234a2891b88356dc06e6d66"},{"url":"https://git.kernel.org/stable/c/b880df0e487caa85c3c7ffda37dcd05334b1aa80"},{"url":"https://git.kernel.org/stable/c/d8a24b9e1774a93943caf68d48c5e17be432220b"},{"url":"https://git.kernel.org/stable/c/31c7b15b3716e8d0dad58d2c3cdf321dfd06f4be"},{"url":"https://git.kernel.org/stable/c/3efe0e0944157fdd2072b4dc7eb0491a317ed272"},{"url":"https://git.kernel.org/stable/c/00fbf71e74115f7628fc0880b855434b1e70c40c"},{"url":"https://git.kernel.org/stable/c/28bc1ef699610ee09ce3d46a00552f5a0a0144bd"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:41:06.206Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10","versionEndExcluding":"5.10.273"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10","versionEndExcluding":"5.15.224"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10","versionEndExcluding":"6.12.113"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10","versionEndExcluding":"6.18.57"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10","versionEndExcluding":"7.2.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10","versionEndExcluding":"7.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9.13"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}