# CVE-2024-56636: geneve: do not assume mac header is set in geneve_xmit_skb()

> A null pointer dereference in the Linux kernel's GENEVE driver can cause a system crash when processing network packets.

- **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:** BELL-CVE-2024-56636, DEBIAN-CVE-2024-56636, GHSA-w8fg-7596-644q, UBUNTU-CVE-2024-56636

## What is CVE-2024-56636?

CVE-2024-56636 is a medium-severity 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:

geneve: do not assume mac header is set in geneve_xmit_skb()

We should not assume mac header is set in output path.

Use skb_eth_hdr() instead of eth_hdr() to fix the issue.

sysbot reported the following :

 WARNING: CPU: 0 PID: 11635 at include/linux/skbuff.h:3052 skb_mac_header include/linux/skbuff.h:3052 [inline]
 WARNING: CPU: 0 PID: 11635 at include/linux/skbuff.h:3052 eth_hdr include/linux/if_ether.h:24 [inline]
 WARNING: CPU: 0 PID: 11635 at include/linux/skbuff.h:3052 geneve_xmit_skb drivers/net/geneve.c:898 [inline]
 WARNING: CPU: 0 PID: 11635 at include/linux/skbuff.h:3052 geneve_xmit+0x4c38/0x5730 drivers/net/geneve.c:1039
Modules linked in:
CPU: 0 UID: 0 PID: 11635 Comm: syz.4.1423 Not tainted 6.12.0-syzkaller-10296-gaaf20f870da0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
 RIP: 0010:skb_mac_header include/linux/skbuff.h:3052 [inline]
 RIP: 0010:eth_hdr include/linux/if_ether.h:24 [inline]
 RIP: 0010:geneve_xmit_skb drivers/net/geneve.c:898 [inline]
 RIP: 0010:geneve_xmit+0x4c38/0x5730 drivers/net/geneve.c:1039
Code: 21 c6 02 e9 35 d4 ff ff e8 a5 48 4c fb 90 0f 0b 90 e9 fd f5 ff ff e8 97 48 4c fb 90 0f 0b 90 e9 d8 f5 ff ff e8 89 48 4c fb 90 <0f> 0b 90 e9 41 e4 ff ff e8 7b 48 4c fb 90 0f 0b 90 e9 cd e7 ff ff
RSP: 0018:ffffc90003b2f870 EFLAGS: 00010283
RAX: 000000000000037a RBX: 000000000000ffff RCX: ffffc9000dc3d000
RDX: 0000000000080000 RSI: ffffffff86428417 RDI: 0000000000000003
RBP: ffffc90003b2f9f0 R08: 0000000000000003 R09: 000000000000ffff
R10: 000000000000ffff R11: 0000000000000002 R12: ffff88806603c000
R13: 0000000000000000 R14: ffff8880685b2780 R15: 0000000000000e23
FS:  00007fdc2deed6c0(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30a1dff8 CR3: 0000000056b8c000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
  __netdev_start_xmit include/linux/netdevice.h:5002 [inline]
  netdev_start_xmit include/linux/netdevice.h:5011 [inline]
  __dev_direct_xmit+0x58a/0x720 net/core/dev.c:4490
  dev_direct_xmit include/linux/netdevice.h:3181 [inline]
  packet_xmit+0x1e4/0x360 net/packet/af_packet.c:285
  packet_snd net/packet/af_packet.c:3146 [inline]
  packet_sendmsg+0x2700/0x5660 net/packet/af_packet.c:3178
  sock_sendmsg_nosec net/socket.c:711 [inline]
  __sock_sendmsg net/socket.c:726 [inline]
  __sys_sendto+0x488/0x4f0 net/socket.c:2197
  __do_sys_sendto net/socket.c:2204 [inline]
  __se_sys_sendto net/socket.c:2200 [inline]
  __x64_sys_sendto+0xe0/0x1c0 net/socket.c:2200
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

## Which versions are affected by CVE-2024-56636?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-56636?

Apply the vendor's patch.

## Is CVE-2024-56636 being exploited?

There is no known exploitation of CVE-2024-56636 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-2024-56636 and fix it if it is affected.

What it is: CVE-2024-56636 is a medium-severity 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-2024-56636 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-2024-56636/ (Markdown: https://insights.sbomify.com/CVE-2024-56636/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-56636
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-56636
- OSV: https://osv.dev/vulnerability/CVE-2024-56636

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-56636/
Summaries are generated and may contain mistakes; the official description above is the record.