CRITICAL Introduced in 5.18
veth FragList Crash
CVE-2026-74476
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
KernelScan AI8.7HIGH
01Description
In the Linux kernel, the following vulnerability has been resolved: veth: convert frag_list skbs before running XDP A frag_list skb can reach veth with data_len set but nr_frags zero. veth_convert_skb_to_xdp_buff() only converts skbs that are shared, locked, have frags[], or do not have enough headroom. It later uses skb_is_nonlinear() to decide whether to set XDP_FLAGS_HAS_FRAGS and xdp_frags_size. That exposes frag_list data to XDP as if it were stored in frags[], but frags[] is empty. AF_XDP copy mode can then trust the bogus XDP fragment metadata, walk an empty fragment entry, and crash in memcpy() from __xsk_rcv(). Route non-linear skbs through skb_pp_cow_data() before exposing them to XDP, and only advertise XDP frags when the resulting skb has frags[]. skb_copy_bits() already handles frag_list input, and skb_pp_cow_data() builds frags[] output with skb_add_rx_frag(), which is the representation XDP multi-buffer expects.
02KernelScan AI Analysis
Risk summary
A local attacker — typically a container workload — can crash the host kernel by sending network traffic through a veth pair that has an XDP program attached. The crash occurs because frag_list packets are incorrectly advertised to XDP as having fragments when the frags[] array is empty. Any deployment using veth with XDP (common in container networking and bridge configurations) is affected.
Vulnerability analysis
When a veth device with an attached XDP program receives a packet whose data is stored in a linked list of sub-buffers rather than in the standard fragment array, the routine that prepares the packet for XDP only checks whether the fragment array has entries — not whether the packet uses the linked-list form. The packet passes through unconverted but is advertised to XDP as having fragments, even though the fragment array is empty. AF_XDP copy mode then trusts this bogus fragment metadata, walks the empty fragment entry, and crashes the kernel. The fix routes all non-linear packets through a copy routine that rebuilds them with proper fragment array entries before exposing them to XDP, and only advertises XDP fragments when the fragment array actually contains entries. Any local process that can send traffic through a veth pair — typically a container workload — can trigger this, provided an XDP program is attached to the receiving veth device. The XDP attachment itself requires administrator privileges to configure, but triggering the crash only requires sending ordinary network traffic.
Lifecycle
03Fix Versions
| Branch | Introduced | Fixed in | Patch commit |
|---|---|---|---|
| 6.1 | 5.18 | 6.1.184 | 0be3632597b8 |
| 6.6 | 5.18 | 6.6.153 | 04958dba44dc |
| 6.12 | 5.18 | 6.12.103 | 5c1c15c540fc |
| 6.18 | 5.18 | 6.18.44 | b24ba0bbffe3 |
| 7.1 | 5.18 | 7.1.8 | f9c1fff857e9 |
| mainline | 5.18 | 7.2 | d0d641596304 |