CVE-2025-68232veth: more robust handing of race to avoid txq getting stuck

Description

In the Linux kernel, the following vulnerability has been resolved: veth: more robust handing of race to avoid txq getting stuck Commit dc82a33297fc ("veth: apply qdisc backpressure on full ptr_ring to reduce TX drops") introduced a race condition that can lead to a permanently stalled TXQ. This was observed in production on ARM64 systems (Ampere Altra Max). The race occurs in veth_xmit(). The producer observes a full ptr_ring and stops the queue (netif_tx_stop_queue()). The subsequent conditional logic, intended to re-wake the queue if the consumer had just emptied it (if (__ptr_ring_empty(...)) netif_tx_wake_queue()), can fail. This leads to a "lost wakeup" where the TXQ remains stopped (QUEUE_STATE_DRV_XOFF) and traffic halts. This failure is caused by an incorrect use of the __ptr_ring_empty() API from the producer side. As noted in kernel comments, this check is not guaranteed to be correct if a consumer is operating on another CPU. The empty test is based on ptr_ring->consumer_head, making it reliable only for the consumer. Using this check from the producer side is fundamentally racy. This patch fixes the race by adopting the more robust logic from an earlier version V4 of the patchset, which always flushed the peer: (1) In veth_xmit(), the racy conditional wake-up logic and its memory barrier are removed. Instead, after stopping the queue, we unconditionally call __veth_xdp_flush(rq). This guarantees that the NAPI consumer is scheduled, making it solely responsible for re-waking the TXQ. This handles the race where veth_poll() consumes all packets and completes NAPI *before* veth_xmit() on the producer side has called netif_tx_stop_queue. The __veth_xdp_flush(rq) will observe rx_notify_masked is false and schedule NAPI. (2) On the consumer side, the logic for waking the peer TXQ is moved out of veth_xdp_rcv() and placed at the end of the veth_poll() function. This placement is part of fixing the race, as the netif_tx_queue_stopped() check must occur after rx_notify_masked is potentially set to false during NAPI completion. This handles the race where veth_poll() consumes all packets, but haven't finished (rx_notify_masked is still true). The producer veth_xmit() stops the TXQ and __veth_xdp_flush(rq) will observe rx_notify_masked is true, meaning not starting NAPI. Then veth_poll() change rx_notify_masked to false and stops NAPI. Before exiting veth_poll() will observe TXQ is stopped and wake it up.

Timeline

Scores

EPSS (exploitation in 30 days)

0.40% · top 65% of all CVEs (13 Nov 2026)

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.

Affected products

• Linux · Linux

  • affected 9fe31b3f314534e238aa6d0b6fb492134cbcf8be – < dd419a3f2ebc18cc00bc32c57fd052d7a188b78b
  • affected dc82a33297fc2c58cb0b2b008d728668d45c0f6a – < 6c8a8b9257a660e622689e23c8fbad4ba2b561b9
  • affected dc82a33297fc2c58cb0b2b008d728668d45c0f6a – < 5442a9da69789741bfda39f34ee7f69552bf0c56

• Linux · Linux

  • affected 6.16
  • unaffected < 6.16
  • unaffected 6.17.10 – ≤ 6.17.*
  • unaffected 6.18 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2025-203664 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2025-68232](https://cveledger.app/badge/CVE-2025-68232.svg)](https://cveledger.app/cve/CVE-2025-68232)

Record last updated 5 Aug 2026, 12:10 UTC.