# CVE-2025-38622: net: drop UFO packets in udp_rcv_segment()

> A local attacker can cause a kernel crash by sending malformed UDP packets with specific GSO settings to a tun device.

- **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:** 22 Aug 2025
- **Updated:** 11 May 2026
- **Also known as:** AZL-66599, AZL-73617, BELL-CVE-2025-38622, DEBIAN-CVE-2025-38622, GHSA-mrx6-v6w2-5q3x, ROOT-OS-DEBIAN-11-CVE-2025-38622, ROOT-OS-DEBIAN-12-CVE-2025-38622, ROOT-OS-DEBIAN-13-CVE-2025-38622, ROOT-OS-UBUNTU-2204-CVE-2025-38622, ROOT-OS-UBUNTU-2404-CVE-2025-38622, UBUNTU-CVE-2025-38622

## What is CVE-2025-38622?

CVE-2025-38622 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 22 Aug 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: drop UFO packets in udp_rcv_segment()

When sending a packet with virtio_net_hdr to tun device, if the gso_type
in virtio_net_hdr is SKB_GSO_UDP and the gso_size is less than udphdr
size, below crash may happen.

  ------------[ cut here ]------------
  kernel BUG at net/core/skbuff.c:4572!
  Oops: invalid opcode: 0000 [#1] SMP NOPTI
  CPU: 0 UID: 0 PID: 62 Comm: mytest Not tainted 6.16.0-rc7 #203 PREEMPT(voluntary)
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
  RIP: 0010:skb_pull_rcsum+0x8e/0xa0
  Code: 00 00 5b c3 cc cc cc cc 8b 93 88 00 00 00 f7 da e8 37 44 38 00 f7 d8 89 83 88 00 00 00 48 8b 83 c8 00 00 00 5b c3 cc cc cc cc <0f> 0b 0f 0b 66 66 2e 0f 1f 84 00 000
  RSP: 0018:ffffc900001fba38 EFLAGS: 00000297
  RAX: 0000000000000004 RBX: ffff8880040c1000 RCX: ffffc900001fb948
  RDX: ffff888003e6d700 RSI: 0000000000000008 RDI: ffff88800411a062
  RBP: ffff8880040c1000 R08: 0000000000000000 R09: 0000000000000001
  R10: ffff888003606c00 R11: 0000000000000001 R12: 0000000000000000
  R13: ffff888004060900 R14: ffff888004050000 R15: ffff888004060900
  FS:  000000002406d3c0(0000) GS:ffff888084a19000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000000020000040 CR3: 0000000004007000 CR4: 00000000000006f0
  Call Trace:
   <TASK>
   udp_queue_rcv_one_skb+0x176/0x4b0 net/ipv4/udp.c:2445
   udp_queue_rcv_skb+0x155/0x1f0 net/ipv4/udp.c:2475
   udp_unicast_rcv_skb+0x71/0x90 net/ipv4/udp.c:2626
   __udp4_lib_rcv+0x433/0xb00 net/ipv4/udp.c:2690
   ip_protocol_deliver_rcu+0xa6/0x160 net/ipv4/ip_input.c:205
   ip_local_deliver_finish+0x72/0x90 net/ipv4/ip_input.c:233
   ip_sublist_rcv_finish+0x5f/0x70 net/ipv4/ip_input.c:579
   ip_sublist_rcv+0x122/0x1b0 net/ipv4/ip_input.c:636
   ip_list_rcv+0xf7/0x130 net/ipv4/ip_input.c:670
   __netif_receive_skb_list_core+0x21d/0x240 net/core/dev.c:6067
   netif_receive_skb_list_internal+0x186/0x2b0 net/core/dev.c:6210
   napi_complete_done+0x78/0x180 net/core/dev.c:6580
   tun_get_user+0xa63/0x1120 drivers/net/tun.c:1909
   tun_chr_write_iter+0x65/0xb0 drivers/net/tun.c:1984
   vfs_write+0x300/0x420 fs/read_write.c:593
   ksys_write+0x60/0xd0 fs/read_write.c:686
   do_syscall_64+0x50/0x1c0 arch/x86/entry/syscall_64.c:63
   </TASK>

To trigger gso segment in udp_queue_rcv_skb(), we should also set option
UDP_ENCAP_ESPINUDP to enable udp_sk(sk)->encap_rcv. When the encap_rcv
hook return 1 in udp_queue_rcv_one_skb(), udp_csum_pull_header() will try
to pull udphdr, but the skb size has been segmented to gso size, which
leads to this crash.

Previous commit cf329aa42b66 ("udp: cope with UDP GRO packet misdirection")
introduces segmentation in UDP receive path only for GRO, which was never
intended to be used for UFO, so drop UFO packets in udp_rcv_segment().

## Which versions are affected by CVE-2025-38622?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-38622?

Apply the vendor's patch.

## Is CVE-2025-38622 being exploited?

There is no known exploitation of CVE-2025-38622 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-38622 and fix it if it is affected.

What it is: CVE-2025-38622 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 22 Aug 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-2025-38622 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2025-38622/ (Markdown: https://insights.sbomify.com/CVE-2025-38622/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-38622
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-38622
- OSV: https://osv.dev/vulnerability/CVE-2025-38622

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-38622/
Summaries are generated and may contain mistakes; the official description above is the record.