CVE-2026-74612
Received Received - Intake

Buffer Overflow in Linux Kernel veth Driver

Publication date: 2026-08-22

Last updated on: 2026-08-22

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: veth: fix skb length accounting after XDP frag adjustment veth exposes non-linear skb fragments through an xdp_buff. If an XDP program adjusts the fragment area, veth_xdp_rcv_skb() copies xdp_frags_size back to skb->data_len but leaves skb->len containing the old fragment contribution. After a fragment shrink, this makes skb_headlen() larger than the actual linear area. In the reproduced UDP receive path, __skb_datagram_iter() copied 1024 bytes past the actual linear tail to userspace, starting at struct skb_shared_info. The copied bytes included the affected skb's nr_frags, xdp_frags_size, and a kernel pointer from skb_shinfo(skb)->frags[0]. Real packet data was displaced by the same amount and truncated at the end. Subtract the old data_len before replacing it and add the new data_len afterwards, keeping skb->len and skb->data_len synchronized. Additionally, bpf_xdp_pull_data() can advance data_end while leaving frags present. The skb is then still non-linear, so the old __skb_put(skb, off) triggers SKB_LINEAR_ASSERT(). Use skb_set_tail_pointer() and update skb->len explicitly instead, following bpf_prog_run_generic_xdp(). Unlike __skb_put(), skb_set_tail_pointer() does not require a linear skb. A 60000-byte UDP datagram on a veth pair with MTU 64000 was shortened by 1024 bytes from its fragment area. Before the fix, all 10 runs produced corrupted payloads. After the fix, all 10 runs matched the expected payload exactly. A forced-tailroom reproducer also exercises bpf_xdp_pull_data() with frags still present; the old code triggers SKB_LINEAR_ASSERT(), while this fix passes 10/10 runs.

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Meta Information

Published
2026-08-22
Last Modified
2026-08-22
Generated
2026-08-22
AI Q&A
2026-08-22
EPSS Evaluated
N/A
NVD
CVE-2026-74612
EUVD
EUVD-2026-64549

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux_kernel linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves incorrect accounting of skb (socket buffer) data length after XDP (eXpress Data Path) fragment adjustments in the veth driver. When an XDP program modifies the fragment area, the kernel fails to properly update skb->len and skb->data_len, causing skb_headlen() to report an incorrect linear data size. This leads to copying of unrelated memory, including kernel pointers, to userspace instead of actual packet data.

Detection Guidance

This vulnerability affects the Linux kernel's veth driver and involves incorrect skb length accounting after XDP fragment adjustment. Detection requires checking kernel logs for corruption in UDP datagrams or kernel pointer leaks in network traffic. Monitor for corrupted payloads or unexpected kernel memory exposure in network captures.

Impact Analysis

This vulnerability could allow an attacker to read sensitive kernel memory or corrupt network packet data when using veth interfaces with XDP programs. It may result in data leaks, crashes, or incorrect processing of network traffic, potentially affecting system stability and security.

Mitigation Strategies

Apply the Linux kernel patch that fixes the veth skb length accounting issue. Update to a kernel version containing the fix or backport the patch. Restart affected systems to ensure the updated kernel is active. Monitor network traffic for signs of corruption or leaks after patching.

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