net, hsr: reject HSR frame if skb can't hold tag

Summary

In the Linux kernel, the following vulnerability has been resolved: net, hsr: reject HSR frame if skb can't hold tag Receiving HSR frame with insufficient space to hold HSR tag in the skb can result in a crash (kernel BUG): [ 45.390915] skbuff: skb_under_panic: text:ffffffff86f32cac len:26 put:14 head:ffff888042418000 data:ffff888042417ff4 tail:0xe end:0x180 dev:bridge_slave_1 [ 45.392559] ------------[ cut here ]------------ [ 45.392912] kernel BUG at net/core/skbuff.c:211! [ 45.393276] Oops: invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI [ 45.393809] CPU: 1 UID: 0 PID: 2496 Comm: reproducer Not tainted 6.15.0 #12 PREEMPT(undef) [ 45.394433] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 45.395273] RIP: 0010:skb_panic+0x15b/0x1d0 <snip registers, remove unreliable trace> [ 45.402911] Call Trace: [ 45.403105] <IRQ> [ 45.404470] skb_push+0xcd/0xf0 [ 45.404726] br_dev_queue_push_xmit+0x7c/0x6c0 [ 45.406513] br_forward_finish+0x128/0x260 [ 45.408483] __br_forward+0x42d/0x590 [ 45.409464] maybe_deliver+0x2eb/0x420 [ 45.409763] br_flood+0x174/0x4a0 [ 45.410030] br_handle_frame_finish+0xc7c/0x1bc0 [ 45.411618] br_handle_frame+0xac3/0x1230 [ 45.413674] __netif_receive_skb_core.constprop.0+0x808/0x3df0 [ 45.422966] __netif_receive_skb_one_core+0xb4/0x1f0 [ 45.424478] __netif_receive_skb+0x22/0x170 [ 45.424806] process_backlog+0x242/0x6d0 [ 45.425116] __napi_poll+0xbb/0x630 [ 45.425394] net_rx_action+0x4d1/0xcc0 [ 45.427613] handle_softirqs+0x1a4/0x580 [ 45.427926] do_softirq+0x74/0x90 [ 45.428196] </IRQ> This issue was found by syzkaller. The panic happens in br_dev_queue_push_xmit() once it receives a corrupted skb with ETH header already pushed in linear data. When it attempts the skb_push() call, there's not enough headroom and skb_push() panics. The corrupted skb is put on the queue by HSR layer, which makes a sequence of unintended transformations when it receives a specific corrupted HSR frame (with incomplete TAG). Fix it by dropping and consuming frames that are not long enough to contain both ethernet and hsr headers. Alternative fix would be to check for enough headroom before skb_push() in br_dev_queue_push_xmit(). In the reproducer, this is injected via AF_PACKET, but I don't easily see why it couldn't be sent over the wire from adjacent network. Further Details: In the reproducer, the following network interface chain is set up: ┌────────────────┐ ┌────────────────┐ │ veth0_to_hsr ├───┤ hsr_slave0 ┼───┐ └────────────────┘ └────────────────┘ │ │ ┌──────┐ ├─┤ hsr0 ├───┐ │ └──────┘ │ ┌────────────────┐ ┌────────────────┐ │ │┌────────┐ │ veth1_to_hsr ┼───┤ hsr_slave1 ├───┘ └┤ │ └────────────────┘ └────────────────┘ ┌┼ bridge │ ││ │ │└────────┘ │ ┌───────┐ │ │ ... ├──────┘ └───────┘ To trigger the events leading up to crash, reproducer sends a corrupted HSR fr ---truncated---

Timeline

1. Sep 5, 2025, 5:21 PM UTCCVE published
2. Oct 15, 2026, 9:53 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: total

3. Oct 15, 2026, 10:02 PM UTCRecord last updated

Affected versions

• Linux Linux

  From f6442ee08fe66c8e45c4f246531a2aaf4f17a7a7 · fixed in 8d9bc4a375a1ba05f7dfa0407de8e510ab9bd14d; From 48b491a5cc74333c4a6a82fe21cea42c055a3b0b · fixed in 3ae272ab523dd6bdc26e879027ed79feac9dd1b3; From 48b491a5cc74333c4a6a82fe21cea42c055a3b0b · fixed in b640188b8a6690e685939053c7efdbc7818b5f4e; From 48b491a5cc74333c4a6a82fe21cea42c055a3b0b · fixed in b117c41b00902c1a7e24347c405cb82504aeae0b; From 48b491a5cc74333c4a6a82fe21cea42c055a3b0b · fixed in acd69b597bd3f76d3b3d322b84082226c00eeaa4; From 48b491a5cc74333c4a6a82fe21cea42c055a3b0b · fixed in 61009439e4bd8d74e705ee15940760321be91d8a; From 48b491a5cc74333c4a6a82fe21cea42c055a3b0b · fixed in 7af76e9d18a9fd6f8611b3313c86c190f9b6a5a7; From 5.10.42 · fixed in 5.10.241; From 5.12.9 · fixed in 5.13

• Linux Linux

  5.13

• KernelLinux

  fixed in 5.10.241; From 5.11.0 · fixed in 5.15.190; From 5.13.0 · fixed in 6.1.149; From 5.16.0 · fixed in 6.6.103; From 6.2.0 · fixed in 6.12.44; From 6.7.0 · fixed in 6.16.4

References 7