CVE-2026-74698
Received Received - Intake

BQL Reset Flaw in Linux Kernel mlx5e 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: net/mlx5e: fix BQL reset on SQ re-activation mlx5e_queue_start() deactivates and re-activates all channels but closes only the queue being restarted. mlx5e_activate_txqsq() then unconditionally calls netdev_tx_reset_queue(), zeroing the BQL counters of channels that kept their in-flight TX WQEs. The next completion then over-charges and trips the BUG_ON() in dql_completed(): kernel BUG at lib/dynamic_queue_limits.c:99! RIP: 0010:dql_completed+0x23d/0x280 Call Trace: <IRQ> mlx5e_poll_tx_cq+0x668/0xa60 mlx5e_napi_poll+0x5b/0x7b0 net_rx_action+0x15a/0x580 Reset BQL only when the SQ has no bytes in flight (sq->cc == sq->pc). In the case that reset is skipped, the outstanding WQEs will eventually complete and rebalance the dql. The dql->limit is carried across the reset.

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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-2026-74698
EUVD
EUVD-2026-64385

Affected Vendors & Products

Currently, no data is known.

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves incorrect handling of Byte Queue Limits (BQL) during network queue restart. When a queue is restarted, BQL counters for other active channels are incorrectly reset, leading to overcharging and a kernel bug check (BUG_ON) in dynamic queue limits.

Detection Guidance

This vulnerability is specific to the Linux kernel's mlx5e driver and may not have direct detection commands. Monitor kernel logs for BUG_ON() errors in dql_completed() or crashes in mlx5e_poll_tx_cq. Check for TX queue issues using ethtool or dmesg after network load.

Impact Analysis

This could cause kernel crashes or instability when network traffic is processed, potentially leading to system freezes or reboots. It affects systems using the mlx5e driver for Mellanox network interfaces.

Mitigation Strategies

Apply the latest kernel updates from your Linux distribution to ensure the fix is included. Restart affected network services or reboot the system if required. Monitor network performance and kernel logs for signs of instability.

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