CVE-2025-38622
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-08-22

Last updated on: 2025-11-03

Assigner: kernel.org

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().
CVSS Scores
EPSS Scores
Probability:
Percentile:
Meta Information
Published
2025-08-22
Last Modified
2025-11-03
Generated
2026-05-27
AI Q&A
2025-08-22
EPSS Evaluated
2026-05-25
NVD
CVE-2025-38622
Affected Vendors & Products
Showing 3 associated CPEs
Vendor Product Version / Range
linux kernel 5.10.244-1
linux kernel 6.16.0-rc7
linux kernel 6.1.153-1
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability occurs in the Linux kernel's network stack when handling UDP packets with a specific configuration. If a packet with a virtio_net_hdr is sent to a tun device with the gso_type set to SKB_GSO_UDP and the gso_size is smaller than the UDP header size, it can cause a kernel crash (BUG) due to invalid memory operations during packet segmentation and checksum processing. This happens because the UDP segmentation offload (UFO) packets are not properly handled in the udp_rcv_segment() function, leading to a crash when the kernel tries to pull the UDP header from a segmented packet that is too small. The issue was fixed by dropping UFO packets in udp_rcv_segment() to prevent this crash.


How can this vulnerability impact me? :

This vulnerability can cause a denial of service by crashing the Linux kernel when processing specially crafted UDP packets under certain conditions. An attacker could exploit this to cause system instability or downtime by triggering the kernel BUG, potentially affecting availability of services running on the affected system.


How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability can be detected by monitoring for kernel crashes or BUG messages related to net/core/skbuff.c, specifically at skb_pull_rcsum. Checking system logs (e.g., dmesg or /var/log/kern.log) for crash signatures like 'kernel BUG at net/core/skbuff.c:4572' or 'Oops: invalid opcode' after sending packets with virtio_net_hdr to tun devices may indicate exploitation attempts. There are no specific commands provided to detect this vulnerability directly.


What immediate steps should I take to mitigate this vulnerability?

Immediate mitigation involves applying the patch that drops UFO packets in udp_rcv_segment(), as introduced in the fix. Until the patch is applied, avoid sending packets with virtio_net_hdr where gso_type is SKB_GSO_UDP and gso_size is less than the UDP header size to tun devices. Also, disabling the UDP_ENCAP_ESPINUDP option to prevent triggering the vulnerable code path may help mitigate the issue.


Ask Our AI Assistant
Need more information? Ask your question to get an AI reply (Powered by our expertise)
0/70
EPSS Chart