net/packet: guard the ll header push in packet_rcv_spkt()
Summary
| CVE | CVE-2026-99033 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-10-23 13:17:26 UTC |
| Updated | 2026-10-30 13:21:40 UTC |
| Description | In the Linux kernel, the following vulnerability has been resolved: net/packet: guard the ll header push in packet_rcv_spkt() packet_rcv_spkt() restores the link layer header with skb_push(skb, skb->data - skb_mac_header(skb)); That subtraction is only meaningful when the device actually has a link layer header. packet_rcv() and tpacket_rcv() both wrap it in dev_has_header(), which is also the predicate the block comment at the top of the file states the restore in terms of; packet_rcv_spkt() does not. commit d549699048b4 ("net/packet: fix packet receive on L3 devices without visible hard header") introduced the helper and changed the two call sites, and this one stayed behind. A device without a visible ll header can leave skb->mac_header at the 0xFFFF sentinel that __alloc_skb() initialises it to. A CAN skb does: init_can_skb() sets pkt_type and ip_summed but does not reset the headers, and commit 9f10374bb024 ("can: remove private CAN skb headroom infrastructure") dropped the skb_reset_*_header() calls that used to be there. skb_mac_header() is then 0xFFFF, the length becomes a large negative number and skb_push() reports it through skb_under_panic() -- from softirq context, so it is a full system panic even with panic_on_oops=0: skbuff: skb_under_panic: text:ffffffff8bd21bc1 len:-65455 put:-65471 head:... data:... tail:0x50 end:0x180 dev:can0 kernel BUG at net/core/skbuff.c:214! RIP: 0010:skb_panic+0x50/0x60 Call Trace: <IRQ> skb_push+0x38/0x40 packet_rcv_spkt+0xe1/0x170 __netif_receive_skb_core.constprop.0+0x7e8/0xd30 ... Kernel panic - not syncing: Fatal exception in interrupt The socket type is reachable: packet_create() accepts SOCK_PACKET alongside SOCK_RAW and SOCK_DGRAM behind the same CAP_NET_RAW check, and neither the socket length nor a capability check keeps it away from a CAN interface. The missing skb_reset_*_header() calls in init_can_skb() are a regression in their own right and are being fixed separately, but a packet socket should not turn a link layer that did not initialise its mac header into a kernel panic. Guard the push the way the other two receive paths do. Tested on v7.3-rc5 under QEMU with a slcan device on a pty, which is the driver RX path: vcan does not reproduce it, because can_send() resets the headers on the way out. One SOCK_PACKET socket bound to can0 and one frame written into the line discipline panics an unpatched kernel with the trace above; the same image with this patch prints no panic and powers off normally. Both kernels are this tree, defconfig plus CONFIG_CAN_SLCAN=y, differing only in this hunk. |
Risk And Classification
EPSS: 0.001850000 probability, percentile 0.081200000 (date 2026-11-01)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected d549699048b4b5c22dd710455bcdb76966e55aa3 48aa1155fa8d83362fc33d02d527a3c3fe40ce1c git | Not specified |
| CNA | Linux | Linux | affected d549699048b4b5c22dd710455bcdb76966e55aa3 7f84ed94ccfe36091234a2891b88356dc06e6d66 git | Not specified |
| CNA | Linux | Linux | affected d549699048b4b5c22dd710455bcdb76966e55aa3 b880df0e487caa85c3c7ffda37dcd05334b1aa80 git | Not specified |
| CNA | Linux | Linux | affected d549699048b4b5c22dd710455bcdb76966e55aa3 d8a24b9e1774a93943caf68d48c5e17be432220b git | Not specified |
| CNA | Linux | Linux | affected d549699048b4b5c22dd710455bcdb76966e55aa3 31c7b15b3716e8d0dad58d2c3cdf321dfd06f4be git | Not specified |
| CNA | Linux | Linux | affected d549699048b4b5c22dd710455bcdb76966e55aa3 3efe0e0944157fdd2072b4dc7eb0491a317ed272 git | Not specified |
| CNA | Linux | Linux | affected d549699048b4b5c22dd710455bcdb76966e55aa3 00fbf71e74115f7628fc0880b855434b1e70c40c git | Not specified |
| CNA | Linux | Linux | affected d549699048b4b5c22dd710455bcdb76966e55aa3 28bc1ef699610ee09ce3d46a00552f5a0a0144bd git | Not specified |
| CNA | Linux | Linux | affected dadddde259a19105ee69e788835f4d4552767aa9 git | Not specified |
| CNA | Linux | Linux | affected 5.9.13 5.10 semver | Not specified |
| CNA | Linux | Linux | affected 5.10 | Not specified |
| CNA | Linux | Linux | unaffected 5.10 semver | Not specified |
| CNA | Linux | Linux | unaffected 5.10.273 5.10.* semver | Not specified |
| CNA | Linux | Linux | unaffected 5.15.224 5.15.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.1.191 6.1.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.6.160 6.6.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.12.113 6.12.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18.57 6.18.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.2.11 7.2.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.3 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/28bc1ef699610ee09ce3d46a00552f5a0a0144bd | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/b880df0e487caa85c3c7ffda37dcd05334b1aa80 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/48aa1155fa8d83362fc33d02d527a3c3fe40ce1c | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/00fbf71e74115f7628fc0880b855434b1e70c40c | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/3efe0e0944157fdd2072b4dc7eb0491a317ed272 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/d8a24b9e1774a93943caf68d48c5e17be432220b | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/31c7b15b3716e8d0dad58d2c3cdf321dfd06f4be | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/7f84ed94ccfe36091234a2891b88356dc06e6d66 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.