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

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Summary

CVECVE-2025-39703
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-09-05 18:15:47 UTC
Updated2026-05-12 13:17:06 UTC
DescriptionIn 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---

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem Types: CWE-476

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected f6442ee08fe66c8e45c4f246531a2aaf4f17a7a7 8d9bc4a375a1ba05f7dfa0407de8e510ab9bd14d git Not specified
CNA Linux Linux affected 48b491a5cc74333c4a6a82fe21cea42c055a3b0b 3ae272ab523dd6bdc26e879027ed79feac9dd1b3 git Not specified
CNA Linux Linux affected 48b491a5cc74333c4a6a82fe21cea42c055a3b0b b640188b8a6690e685939053c7efdbc7818b5f4e git Not specified
CNA Linux Linux affected 48b491a5cc74333c4a6a82fe21cea42c055a3b0b b117c41b00902c1a7e24347c405cb82504aeae0b git Not specified
CNA Linux Linux affected 48b491a5cc74333c4a6a82fe21cea42c055a3b0b acd69b597bd3f76d3b3d322b84082226c00eeaa4 git Not specified
CNA Linux Linux affected 48b491a5cc74333c4a6a82fe21cea42c055a3b0b 61009439e4bd8d74e705ee15940760321be91d8a git Not specified
CNA Linux Linux affected 48b491a5cc74333c4a6a82fe21cea42c055a3b0b 7af76e9d18a9fd6f8611b3313c86c190f9b6a5a7 git Not specified
CNA Linux Linux affected 4ffd1d4a6b306ff69cbe412d2c54d2dd349ff436 git Not specified
CNA Linux Linux affected 5.13 Not specified
CNA Linux Linux unaffected 5.13 semver Not specified
CNA Linux Linux unaffected 5.10.241 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.190 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.149 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.103 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.44 6.12.* semver Not specified
CNA Linux Linux unaffected 6.16.4 6.16.* semver Not specified
CNA Linux Linux unaffected 6.17 * original_commit_for_fix Not specified
ADP Siemens SIMATIC CN 4100 affected V5.0 custom Not specified

References

ReferenceSourceLinkTags
lists.debian.org/debian-lts-announce/2025/10/msg00008.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org Mailing List, Third Party Advisory
git.kernel.org/stable/c/7af76e9d18a9fd6f8611b3313c86c190f9b6a5a7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/b640188b8a6690e685939053c7efdbc7818b5f4e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/61009439e4bd8d74e705ee15940760321be91d8a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
cert-portal.siemens.com/productcert/html/ssa-032379.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
git.kernel.org/stable/c/8d9bc4a375a1ba05f7dfa0407de8e510ab9bd14d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/3ae272ab523dd6bdc26e879027ed79feac9dd1b3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
lists.debian.org/debian-lts-announce/2025/10/msg00007.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org Mailing List, Third Party Advisory
git.kernel.org/stable/c/b117c41b00902c1a7e24347c405cb82504aeae0b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/acd69b597bd3f76d3b3d322b84082226c00eeaa4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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