# CVE-2025-21790: vxlan: check vxlan_vnigroup_init() return value

> A missing return value check in the Linux kernel VXLAN driver causes a null pointer dereference, leading to a system crash.

- **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 Feb 2025
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-57962, BELL-CVE-2025-21790, DEBIAN-CVE-2025-21790, GHSA-hjrf-48vm-fq22, ROOT-OS-UBUNTU-2404-CVE-2025-21790, UBUNTU-CVE-2025-21790

## What is CVE-2025-21790?

CVE-2025-21790 is a medium-severity vulnerability in Linux kernel, published on 27 Feb 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:

vxlan: check vxlan_vnigroup_init() return value

vxlan_init() must check vxlan_vnigroup_init() success
otherwise a crash happens later, spotted by syzbot.

Oops: general protection fault, probably for non-canonical address 0xdffffc000000002c: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000160-0x0000000000000167]
CPU: 0 UID: 0 PID: 7313 Comm: syz-executor147 Not tainted 6.14.0-rc1-syzkaller-00276-g69b54314c975 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
 RIP: 0010:vxlan_vnigroup_uninit+0x89/0x500 drivers/net/vxlan/vxlan_vnifilter.c:912
Code: 00 48 8b 44 24 08 4c 8b b0 98 41 00 00 49 8d 86 60 01 00 00 48 89 c2 48 89 44 24 10 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 4d 04 00 00 49 8b 86 60 01 00 00 48 ba 00 00 00
RSP: 0018:ffffc9000cc1eea8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000001 RCX: ffffffff8672effb
RDX: 000000000000002c RSI: ffffffff8672ecb9 RDI: ffff8880461b4f18
RBP: ffff8880461b4ef4 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000020000
R13: ffff8880461b0d80 R14: 0000000000000000 R15: dffffc0000000000
FS:  00007fecfa95d6c0(0000) GS:ffff88806a600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fecfa95cfb8 CR3: 000000004472c000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
  vxlan_uninit+0x1ab/0x200 drivers/net/vxlan/vxlan_core.c:2942
  unregister_netdevice_many_notify+0x12d6/0x1f30 net/core/dev.c:11824
  unregister_netdevice_many net/core/dev.c:11866 [inline]
  unregister_netdevice_queue+0x307/0x3f0 net/core/dev.c:11736
  register_netdevice+0x1829/0x1eb0 net/core/dev.c:10901
  __vxlan_dev_create+0x7c6/0xa30 drivers/net/vxlan/vxlan_core.c:3981
  vxlan_newlink+0xd1/0x130 drivers/net/vxlan/vxlan_core.c:4407
  rtnl_newlink_create net/core/rtnetlink.c:3795 [inline]
  __rtnl_newlink net/core/rtnetlink.c:3906 [inline]

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2025-21790?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-21790?

Apply the vendor's patch.

## Is CVE-2025-21790 being exploited?

There is no known exploitation of CVE-2025-21790 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-2025-21790 and fix it if it is affected.

What it is: CVE-2025-21790 is a medium-severity vulnerability in Linux kernel, published on 27 Feb 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-2025-21790 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-2025-21790/ (Markdown: https://insights.sbomify.com/CVE-2025-21790/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21790
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21790
- OSV: https://osv.dev/vulnerability/CVE-2025-21790

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21790/
Summaries are generated and may contain mistakes; the official description above is the record.