# CVE-2024-56659: net: lapb: increase LAPB_HEADER_LEN

> A flaw in the Linux kernel's LAPB network protocol handling can cause a kernel crash, leading to a denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 Dec 2024
- **Updated:** 11 May 2026
- **Also known as:** AZL-54794, AZL-54841, BELL-CVE-2024-56659, DEBIAN-CVE-2024-56659, GHSA-7v7h-rp2j-g295, UBUNTU-CVE-2024-56659

## What is CVE-2024-56659?

CVE-2024-56659 is a medium-severity denial of service vulnerability in Linux kernel, published on 27 Dec 2024. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

net: lapb: increase LAPB_HEADER_LEN

It is unclear if net/lapb code is supposed to be ready for 8021q.

We can at least avoid crashes like the following :

skbuff: skb_under_panic: text:ffffffff8aabe1f6 len:24 put:20 head:ffff88802824a400 data:ffff88802824a3fe tail:0x16 end:0x140 dev:nr0.2
------------[ cut here ]------------
 kernel BUG at net/core/skbuff.c:206 !
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 1 UID: 0 PID: 5508 Comm: dhcpcd Not tainted 6.12.0-rc7-syzkaller-00144-g66418447d27b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
 RIP: 0010:skb_panic net/core/skbuff.c:206 [inline]
 RIP: 0010:skb_under_panic+0x14b/0x150 net/core/skbuff.c:216
Code: 0d 8d 48 c7 c6 2e 9e 29 8e 48 8b 54 24 08 8b 0c 24 44 8b 44 24 04 4d 89 e9 50 41 54 41 57 41 56 e8 1a 6f 37 02 48 83 c4 20 90 <0f> 0b 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3
RSP: 0018:ffffc90002ddf638 EFLAGS: 00010282
RAX: 0000000000000086 RBX: dffffc0000000000 RCX: 7a24750e538ff600
RDX: 0000000000000000 RSI: 0000000000000201 RDI: 0000000000000000
RBP: ffff888034a86650 R08: ffffffff8174b13c R09: 1ffff920005bbe60
R10: dffffc0000000000 R11: fffff520005bbe61 R12: 0000000000000140
R13: ffff88802824a400 R14: ffff88802824a3fe R15: 0000000000000016
FS:  00007f2a5990d740(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c2631fd CR3: 0000000029504000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
  skb_push+0xe5/0x100 net/core/skbuff.c:2636
  nr_header+0x36/0x320 net/netrom/nr_dev.c:69
  dev_hard_header include/linux/netdevice.h:3148 [inline]
  vlan_dev_hard_header+0x359/0x480 net/8021q/vlan_dev.c:83
  dev_hard_header include/linux/netdevice.h:3148 [inline]
  lapbeth_data_transmit+0x1f6/0x2a0 drivers/net/wan/lapbether.c:257
  lapb_data_transmit+0x91/0xb0 net/lapb/lapb_iface.c:447
  lapb_transmit_buffer+0x168/0x1f0 net/lapb/lapb_out.c:149
 lapb_establish_data_link+0x84/0xd0
 lapb_device_event+0x4e0/0x670
  notifier_call_chain+0x19f/0x3e0 kernel/notifier.c:93
 __dev_notify_flags+0x207/0x400
  dev_change_flags+0xf0/0x1a0 net/core/dev.c:8922
  devinet_ioctl+0xa4e/0x1aa0 net/ipv4/devinet.c:1188
  inet_ioctl+0x3d7/0x4f0 net/ipv4/af_inet.c:1003
  sock_do_ioctl+0x158/0x460 net/socket.c:1227
  sock_ioctl+0x626/0x8e0 net/socket.c:1346
  vfs_ioctl fs/ioctl.c:51 [inline]
  __do_sys_ioctl fs/ioctl.c:907 [inline]
  __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83

## Which versions are affected by CVE-2024-56659?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-56659?

Apply the vendor's patch.

## Is CVE-2024-56659 being exploited?

There is no known exploitation of CVE-2024-56659 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-56659 and fix it if it is affected.

What it is: CVE-2024-56659 is a medium-severity denial of service vulnerability in Linux kernel, published on 27 Dec 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2024-56659 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2024-56659/ (Markdown: https://insights.sbomify.com/CVE-2024-56659/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-56659
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-56659
- OSV: https://osv.dev/vulnerability/CVE-2024-56659

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-56659/
Summaries are generated and may contain mistakes; the official description above is the record.