# CVE-2024-56372: net: tun: fix tun_napi_alloc_frags()

> A flaw in the Linux kernel's TUN driver causes a crash when processing network fragments, 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:** 11 Jan 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2024-56372, DEBIAN-CVE-2024-56372, GHSA-f2cp-w9wf-8v89, UBUNTU-CVE-2024-56372

## What is CVE-2024-56372?

CVE-2024-56372 is a medium-severity vulnerability in Linux kernel, published on 11 Jan 2025. 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: tun: fix tun_napi_alloc_frags()

syzbot reported the following crash [1]

Issue came with the blamed commit. Instead of going through
all the iov components, we keep using the first one
and end up with a malformed skb.

[1]

kernel BUG at net/core/skbuff.c:2849 !
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 0 UID: 0 PID: 6230 Comm: syz-executor132 Not tainted 6.13.0-rc1-syzkaller-00407-g96b6fcc0ee41 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024
 RIP: 0010:__pskb_pull_tail+0x1568/0x1570 net/core/skbuff.c:2848
Code: 38 c1 0f 8c 32 f1 ff ff 4c 89 f7 e8 92 96 74 f8 e9 25 f1 ff ff e8 e8 ae 09 f8 48 8b 5c 24 08 e9 eb fb ff ff e8 d9 ae 09 f8 90 <0f> 0b 66 0f 1f 44 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90004cbef30 EFLAGS: 00010293
RAX: ffffffff8995c347 RBX: 00000000fffffff2 RCX: ffff88802cf45a00
RDX: 0000000000000000 RSI: 00000000fffffff2 RDI: 0000000000000000
RBP: ffff88807df0c06a R08: ffffffff8995b084 R09: 1ffff1100fbe185c
R10: dffffc0000000000 R11: ffffed100fbe185d R12: ffff888076e85d50
R13: ffff888076e85c80 R14: ffff888076e85cf4 R15: ffff888076e85c80
FS:  00007f0dca6ea6c0(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0dca6ead58 CR3: 00000000119da000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
  skb_cow_data+0x2da/0xcb0 net/core/skbuff.c:5284
  tipc_aead_decrypt net/tipc/crypto.c:894 [inline]
  tipc_crypto_rcv+0x402/0x24e0 net/tipc/crypto.c:1844
  tipc_rcv+0x57e/0x12a0 net/tipc/node.c:2109
  tipc_l2_rcv_msg+0x2bd/0x450 net/tipc/bearer.c:668
  __netif_receive_skb_list_ptype net/core/dev.c:5720 [inline]
  __netif_receive_skb_list_core+0x8b7/0x980 net/core/dev.c:5762
  __netif_receive_skb_list net/core/dev.c:5814 [inline]
  netif_receive_skb_list_internal+0xa51/0xe30 net/core/dev.c:5905
  gro_normal_list include/net/gro.h:515 [inline]
  napi_complete_done+0x2b5/0x870 net/core/dev.c:6256
  napi_complete include/linux/netdevice.h:567 [inline]
  tun_get_user+0x2ea0/0x4890 drivers/net/tun.c:1982
  tun_chr_write_iter+0x10d/0x1f0 drivers/net/tun.c:2057
 do_iter_readv_writev+0x600/0x880
  vfs_writev+0x376/0xba0 fs/read_write.c:1050
  do_writev+0x1b6/0x360 fs/read_write.c:1096
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2024-56372?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-56372?

Apply the vendor's patch.

## Is CVE-2024-56372 being exploited?

There is no known exploitation of CVE-2024-56372 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-2024-56372 and fix it if it is affected.

What it is: CVE-2024-56372 is a medium-severity vulnerability in Linux kernel, published on 11 Jan 2025. 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-2024-56372 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-2024-56372/ (Markdown: https://insights.sbomify.com/CVE-2024-56372/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-56372
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-56372
- OSV: https://osv.dev/vulnerability/CVE-2024-56372

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-56372/
Summaries are generated and may contain mistakes; the official description above is the record.