CVE-2025-38622

What it is

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().

At a glance

Exploitability

Can be exploited locally on the machine with a low-privilege account. High risk of service disruption.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2025-08-22 16:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-11-05 22:17 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.2% in the next 30 days (EPSS).
• Severity: 5.5 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2025-08-22 16:15 UTC

Last modified

2026-11-05 22:17 UTC

Exploit probability

0.2% · EPSS, next 30 days

Record status

Analyzed

Affected

• Linux Kernel < 5.4.297
• Linux Kernel < 5.10.241
• Linux Kernel < 5.15.190
• Linux Kernel < 6.1.148
• Linux Kernel < 6.6.102
• Linux Kernel < 6.12.42
• Linux Kernel < 6.15.10
• Linux Kernel < 6.16.1

Attack profile CVSS 3.1 · 5.5

Attack vector

Local

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

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