{"id":"AZL-110894","summary":"CVE-2026-99033 affecting package kernel 6.6.157.1-1","details":"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-\u003edata - 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-\u003emac_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   \u003cIRQ\u003e\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.","modified":"2026-10-25T05:30:37Z","published":"2026-10-23T13:17:26Z","upstream":["CVE-2026-99033"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-99033"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"6.6.157.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-110894.json"}}],"schema_version":"1.9.0"}