ghsa-fjf6-f8jx-fjgp
Vulnerability from github
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
[ 45.402911] Call Trace: [ 45.403105] [ 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]
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---
{
"affected": [],
"aliases": [
"CVE-2025-39703"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-09-05T18:15:47Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet, hsr: reject HSR frame if skb can\u0027t hold tag\n\nReceiving HSR frame with insufficient space to hold HSR tag in the skb\ncan result in a crash (kernel BUG):\n\n[ 45.390915] skbuff: skb_under_panic: text:ffffffff86f32cac len:26 put:14 head:ffff888042418000 data:ffff888042417ff4 tail:0xe end:0x180 dev:bridge_slave_1\n[ 45.392559] ------------[ cut here ]------------\n[ 45.392912] kernel BUG at net/core/skbuff.c:211!\n[ 45.393276] Oops: invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI\n[ 45.393809] CPU: 1 UID: 0 PID: 2496 Comm: reproducer Not tainted 6.15.0 #12 PREEMPT(undef)\n[ 45.394433] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014\n[ 45.395273] RIP: 0010:skb_panic+0x15b/0x1d0\n\n\u003csnip registers, remove unreliable trace\u003e\n\n[ 45.402911] Call Trace:\n[ 45.403105] \u003cIRQ\u003e\n[ 45.404470] skb_push+0xcd/0xf0\n[ 45.404726] br_dev_queue_push_xmit+0x7c/0x6c0\n[ 45.406513] br_forward_finish+0x128/0x260\n[ 45.408483] __br_forward+0x42d/0x590\n[ 45.409464] maybe_deliver+0x2eb/0x420\n[ 45.409763] br_flood+0x174/0x4a0\n[ 45.410030] br_handle_frame_finish+0xc7c/0x1bc0\n[ 45.411618] br_handle_frame+0xac3/0x1230\n[ 45.413674] __netif_receive_skb_core.constprop.0+0x808/0x3df0\n[ 45.422966] __netif_receive_skb_one_core+0xb4/0x1f0\n[ 45.424478] __netif_receive_skb+0x22/0x170\n[ 45.424806] process_backlog+0x242/0x6d0\n[ 45.425116] __napi_poll+0xbb/0x630\n[ 45.425394] net_rx_action+0x4d1/0xcc0\n[ 45.427613] handle_softirqs+0x1a4/0x580\n[ 45.427926] do_softirq+0x74/0x90\n[ 45.428196] \u003c/IRQ\u003e\n\nThis issue was found by syzkaller.\n\nThe panic happens in br_dev_queue_push_xmit() once it receives a\ncorrupted skb with ETH header already pushed in linear data. When it\nattempts the skb_push() call, there\u0027s not enough headroom and\nskb_push() panics.\n\nThe corrupted skb is put on the queue by HSR layer, which makes a\nsequence of unintended transformations when it receives a specific\ncorrupted HSR frame (with incomplete TAG).\n\nFix it by dropping and consuming frames that are not long enough to\ncontain both ethernet and hsr headers.\n\nAlternative fix would be to check for enough headroom before skb_push()\nin br_dev_queue_push_xmit().\n\nIn the reproducer, this is injected via AF_PACKET, but I don\u0027t easily\nsee why it couldn\u0027t be sent over the wire from adjacent network.\n\nFurther Details:\n\nIn the reproducer, the following network interface chain is set up:\n\n\u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510 \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510\n\u2502 veth0_to_hsr \u251c\u2500\u2500\u2500\u2524 hsr_slave0 \u253c\u2500\u2500\u2500\u2510\n\u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518 \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518 \u2502\n \u2502 \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2510\n \u251c\u2500\u2524 hsr0 \u251c\u2500\u2500\u2500\u2510\n \u2502 \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2518 \u2502\n\u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510 \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510 \u2502 \u2502\u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510\n\u2502 veth1_to_hsr \u253c\u2500\u2500\u2500\u2524 hsr_slave1 \u251c\u2500\u2500\u2500\u2518 \u2514\u2524 \u2502\n\u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518 \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518 \u250c\u253c bridge \u2502\n \u2502\u2502 \u2502\n \u2502\u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518\n \u2502\n \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510 \u2502\n \u2502 ... \u251c\u2500\u2500\u2500\u2500\u2500\u2500\u2518\n \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518\n\nTo trigger the events leading up to crash, reproducer sends a corrupted\nHSR fr\n---truncated---",
"id": "GHSA-fjf6-f8jx-fjgp",
"modified": "2025-09-05T18:31:27Z",
"published": "2025-09-05T18:31:27Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-39703"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3ae272ab523dd6bdc26e879027ed79feac9dd1b3"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/61009439e4bd8d74e705ee15940760321be91d8a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7af76e9d18a9fd6f8611b3313c86c190f9b6a5a7"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8d9bc4a375a1ba05f7dfa0407de8e510ab9bd14d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/acd69b597bd3f76d3b3d322b84082226c00eeaa4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b117c41b00902c1a7e24347c405cb82504aeae0b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b640188b8a6690e685939053c7efdbc7818b5f4e"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
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