CVE-2026-74742: Linux Vulnerability (CVSS 7.5)

Description

In the Linux kernel, the following vulnerability has been resolved: veth: fix queue index used to wake the peer txq in veth_poll veth_poll() derives the index of the peer TX queue to wake from rq->xdp_rxq.queue_index. That field is only initialized by xdp_rxq_info_reg() in veth_enable_xdp_range(), which runs only when an XDP program is attached. On the plain GRO/NAPI path (veth_napi_enable_range()) xdp_rxq_info_reg() is never called, so queue_index stays 0 for every queue, as priv->rq is zero-allocated. So in a multi-queue setup with GRO enabled and no XDP program attached, every NAPI instance looks at the peer's TX queue 0. If veth_xmit() stops peer TX queue 1 because the ptr_ring is full (NETDEV_TX_BUSY), nothing ever wakes it again: the poller draining queue 1 wakes queue 0 instead. veth implements no ndo_tx_timeout, so the netdev watchdog does not kick in either, and the queue stays stopped indefinitely. Derive the index from the position of the rq within priv->rq instead, which is correct regardless of whether XDP was ever enabled. Scripts to reproduce the stall are available at https://github.com/netoptimizer/veth-backpressure-performance-testing

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 9fe31b3f314534e238aa6d0b6fb492134cbcf8be, < b662a1fb4f3a5ea19bac24eea8315b1d05be51e7; >= dc82a33297fc2c58cb0b2b008d728668d45c0f6a, < 73f8dd22b1e533a99ecc3f9b5de6c6daccaecace; >= dc82a33297fc2c58cb0b2b008d728668d45c0f6a, < 90bb11fb29d3c55a2c46dc7c386d096b286e7fcf; >= dc82a33297fc2c58cb0b2b008d728668d45c0f6a, < 60db47f02bfa2aa688938aa199117ec4f8e31d23; >= 6.12.61, < 6.12.105
Linux	Linux	6.16

References

Timeline

Published: Aug 26, 2026
Last Modified: Aug 27, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-74742?

In the Linux kernel, the following vulnerability has been resolved: veth: fix queue index used to wake the peer txq in veth_poll veth_poll() derives the index of the peer TX queue to wake from rq->xdp_rxq.queue_index. That field is only initialized by xdp_rxq_info_reg() in veth_enable_xdp_range(), which runs only when an XDP program is attached. On the plain GRO/NAPI path (veth_napi_enable_range()) xdp_rxq_info_reg() is never called, so queue_index stays 0 for every queue, as priv->rq is zero-allocated. So in a multi-queue setup with GRO enabled and no XDP program attached, every NAPI instance looks at the peer's TX queue 0. If veth_xmit() stops peer TX queue 1 because the ptr_ring is full (NETDEV_TX_BUSY), nothing ever wakes it again: the poller draining queue 1 wakes queue 0 instead. veth implements no ndo_tx_timeout, so the netdev watchdog does not kick in either, and the queue stays stopped indefinitely. Derive the index from the position of the rq within priv->rq instead, which is correct regardless of whether XDP was ever enabled. Scripts to reproduce the stall are available at https://github.com/netoptimizer/veth-backpressure-performance-testing

How severe is CVE-2026-74742?

CVE-2026-74742 has a CVSS score of 7.5/10 (HIGH severity).

How do I fix CVE-2026-74742?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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