---
id: CVE-2025-38622
title: 'net: drop UFO packets in udp_rcv_segment()'
summary: |-
  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 i…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= cf329aa42b6659204fee865bbce0ea20462552eb <
    72f97d3cb791e26492236b2be7fd70d2c6222555
  - >-
    Linux >= cf329aa42b6659204fee865bbce0ea20462552eb <
    df6ad849d59256dcc0e2234844ef9f0daf885f5c
  - >-
    Linux >= cf329aa42b6659204fee865bbce0ea20462552eb <
    4c1022220b1b6fea802175e80444923a3bbf93a5
  - >-
    Linux >= cf329aa42b6659204fee865bbce0ea20462552eb <
    791f32c5eab33ca3a153f8f6f763aa0df1ddc320
  - >-
    Linux >= cf329aa42b6659204fee865bbce0ea20462552eb <
    0d45954034f8edd6d4052e0190d3d6335c37e4de
  - >-
    Linux >= cf329aa42b6659204fee865bbce0ea20462552eb <
    c0ec2e47f1e92d69b42b17a4a1e543256778393e
  - >-
    Linux >= cf329aa42b6659204fee865bbce0ea20462552eb <
    fc45b3f9599b657d4a64bcf423d2a977b3e13a49
  - >-
    Linux >= cf329aa42b6659204fee865bbce0ea20462552eb <
    0c639c6479ec4480372901a5fc566f7588cf5522
  - >-
    Linux >= cf329aa42b6659204fee865bbce0ea20462552eb <
    d46e51f1c78b9ab9323610feb14238d06d46d519
  - Linux 5.0
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-05T21:05:12.360041Z'
published: '2025-08-22'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T21:12:49.192Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-38622'
references:
  - url: 'https://git.kernel.org/stable/c/72f97d3cb791e26492236b2be7fd70d2c6222555'
  - url: 'https://git.kernel.org/stable/c/df6ad849d59256dcc0e2234844ef9f0daf885f5c'
  - url: 'https://git.kernel.org/stable/c/4c1022220b1b6fea802175e80444923a3bbf93a5'
  - url: 'https://git.kernel.org/stable/c/791f32c5eab33ca3a153f8f6f763aa0df1ddc320'
  - url: 'https://git.kernel.org/stable/c/0d45954034f8edd6d4052e0190d3d6335c37e4de'
  - url: 'https://git.kernel.org/stable/c/c0ec2e47f1e92d69b42b17a4a1e543256778393e'
  - url: 'https://git.kernel.org/stable/c/fc45b3f9599b657d4a64bcf423d2a977b3e13a49'
  - url: 'https://git.kernel.org/stable/c/0c639c6479ec4480372901a5fc566f7588cf5522'
  - url: 'https://git.kernel.org/stable/c/d46e51f1c78b9ab9323610feb14238d06d46d519'
tags:
  - cve.org
epss: 0.00183
epssPercentile: 0.07933
ingestedAt: '2026-11-05T22:38:32.001Z'
---

## Overview

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().

## Affected

- `Linux >= cf329aa42b6659204fee865bbce0ea20462552eb < 72f97d3cb791e26492236b2be7fd70d2c6222555`
- `Linux >= cf329aa42b6659204fee865bbce0ea20462552eb < df6ad849d59256dcc0e2234844ef9f0daf885f5c`
- `Linux >= cf329aa42b6659204fee865bbce0ea20462552eb < 4c1022220b1b6fea802175e80444923a3bbf93a5`
- `Linux >= cf329aa42b6659204fee865bbce0ea20462552eb < 791f32c5eab33ca3a153f8f6f763aa0df1ddc320`
- `Linux >= cf329aa42b6659204fee865bbce0ea20462552eb < 0d45954034f8edd6d4052e0190d3d6335c37e4de`
- `Linux >= cf329aa42b6659204fee865bbce0ea20462552eb < c0ec2e47f1e92d69b42b17a4a1e543256778393e`
- `Linux >= cf329aa42b6659204fee865bbce0ea20462552eb < fc45b3f9599b657d4a64bcf423d2a977b3e13a49`
- `Linux >= cf329aa42b6659204fee865bbce0ea20462552eb < 0c639c6479ec4480372901a5fc566f7588cf5522`
- `Linux >= cf329aa42b6659204fee865bbce0ea20462552eb < d46e51f1c78b9ab9323610feb14238d06d46d519`
- `Linux 5.0`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.