CVE-2026-64210 in Linux
Summary
by MITRE • 07/24/2026
In the Linux kernel, the following vulnerability has been resolved:
net/mlx5e: xsk: Fix unlocked writing to ICOSQ
During napi poll, when the affinity changes and there's still XSK work to be done, we trigger an ICOSQ interrupt on the new CPU. However, this triggering on the ICOSQ is done unprotected.
There are 2 such races:
A) mlx5e_trigger_irq() is called while mlx5e_xsk_alloc_rx_mpwqe() is running from a different CPU due to affinity change. This can happen because IRQ triggering is done after napi_complete_done(). At this point the NAPI can be scheduled on a different CPU. Like this:
CPU A (old affinity, NAPI tail) CPU B (new affinity, fresh NAPI) ------------------------------- -------------------------------- napi_complete_done() clears SCHED mlx5e_cq_arm(...) napi_schedule_prep() sets SCHED mlx5e_napi_poll() mlx5e_xsk_alloc_rx_mpwqe() mlx5e_icosq_sync_lock() // noop memcpy 640 B UMR body advance sq->pc by 10 mlx5e_trigger_irq(&c->icosq) wqe_info[pi] = {NOP, 1}
mlx5e_post_nop() advances sq->pc
B) mlx5e_trigger_irq() is called on the ICOSQ when mlx5e_trigger_napi_icosq() is running.
The obvious fix would be to lock the ICOSQ. But ICOSQ has an optimized locking scheme that doesn't work for this scenario. Kick the async ICOSQ instead which is always locked.
This issue was noticed in the wild with the following splat:
netdevice: ge-0-0-1: Bad OP in ICOSQ CQE: 0xd WARNING: drivers/net/ethernet/mellanox/mlx5/core/en_rx.c:826 [...]
[...]
Call Trace: <IRQ> mlx5e_napi_poll+0x11d/0x7f0 [mlx5_core]
__napi_poll+0x30/0x200 ? skb_defer_free_flush+0x9c/0xc0 net_rx_action+0x2fe/0x3f0 handle_softirqs+0xd8/0x340 __irq_exit_rcu+0xbc/0xe0 common_interrupt+0x85/0xa0 </IRQ> <TASK> asm_common_interrupt+0x26/0x40 [...]
---[ end trace 0000000000000000 ]---
mlx5_core 0000:08:00.0 ge-0-0-1: Error cqe on cqn 0x548, ci 0x2022, qn 0x8f4, opcode 0xd, syndrome 0x2, vendor syndrome 0x68 00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00000030: 00 00 00 00 01 00 68 02 01 00 08 f4 de 14 59 d2 WQE DUMP: WQ size 16384 WQ cur size 0, WQE index 0x1e14, len: 64 00000000: 00 00 00 01 d9 ed 80 02 00 00 00 01 d9 ed 90 02 00000010: 00 00 00 01 d9 ed a0 02 00 00 00 01 d9 ed b0 02 00000020: 00 00 00 01 d9 ed c0 02 00 00 00 01 d9 ed d0 02 00000030: 00 00 00 01 d9 ed e0 02 00 00 00 01 d9 ed f0 02 mlx5_core 0000:08:00.0 ge-0-0-1: Error cqe on cqn 0x548, ci 0x2023, qn 0x8f4, opcode 0xd, syndrome 0x5, vendor syndrome 0xf9 00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00000030: 00 00 00 00 01 00 f9 05 01 00 08 f4 de 15 cf d2
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Analysis
by VulDB Data Team • 07/24/2026
The vulnerability in the Linux kernel's Mellanox mlx5 network driver involves a race condition during interrupt handling for the ICOSQ (Interrupt Coalescing SQ) component. This issue manifests when NAPI polling occurs with changing CPU affinity and concurrent XSK (XDP Socket) work processing, leading to unprotected writes to the ICOSQ structure. The problem specifically affects the mlx5e driver's handling of hardware queue operations in high-performance network environments where multiple CPUs may process network traffic simultaneously.
The core technical flaw stems from unprotected access to the ICOSQ interrupt triggering mechanism during napi poll operations. When CPU affinity changes, the system must migrate NAPI processing to a different CPU while maintaining proper interrupt signaling for the ICOSQ. However, the current implementation allows mlx5e_trigger_irq() to be called without proper synchronization against concurrent operations that may be modifying the same ICOSQ structure. This creates two distinct race conditions where the interrupt triggering can occur during ongoing memory management operations or while other ICOSQ processing is in progress.
The vulnerability is classified as a concurrency issue affecting the kernel's networking subsystem and aligns with CWE-362 (Concurrent Execution using Shared Resource with Unprotected Read-Write Access) and CWE-367 (Time-of-Check to Time-of-Use). The specific operational impact occurs when hardware completion queue entries (CQEs) report error opcodes, particularly opcode 0xd which indicates a bad operation in the ICOSQ. These errors manifest as kernel splats showing "Bad OP in ICOSQ CQE" messages and are typically triggered during high network load conditions where CPU affinity changes occur frequently.
The mitigation strategy involves changing from direct ICOSQ locking to asynchronous ICOSQ handling that always maintains proper locking semantics. This approach leverages existing optimized locking mechanisms within the driver's async processing pathways while avoiding the complex locking schemes that fail in this specific concurrent scenario. The fix addresses both race conditions by ensuring that interrupt triggering operations occur only when appropriate locks are held, preventing the corrupted WQE (Work Queue Element) operations that lead to hardware-level errors.
This vulnerability represents a significant risk in high-performance networking environments where Mellanox network adapters are deployed, particularly affecting systems using XDP with hardware offloading features. The issue impacts system stability and can cause network interface failures under load conditions typical of data center and high-throughput networking scenarios. Security implications extend beyond simple availability concerns to potential denial-of-service conditions that could affect network services and applications relying on consistent hardware behavior. The fix ensures proper synchronization while maintaining the performance characteristics expected from Mellanox's high-speed network drivers, aligning with ATT&CK technique T1498.001 (Direct Network Flood) through improved handling of concurrent network operations that could otherwise be exploited to cause system instability.