CVE-2026-63859 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
net: airoha: Add missing bits in airoha_qdma_cleanup_tx_queue()
Similar to airoha_qdma_cleanup_rx_queue(), reset DMA TX descriptors in airoha_qdma_cleanup_tx_queue routine. Moreover, reset TX_DMA_IDX to TX_CPU_IDX to notify the NIC the QDMA TX ring is empty.
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Analysis
by VulDB Data Team • 07/19/2026
This vulnerability resides within the Linux kernel's networking subsystem, specifically affecting the airoha wireless network driver implementation. The issue manifests in the qdma_cleanup_tx_queue function where insufficient cleanup operations are performed on DMA transmit descriptors. The flaw represents a classic case of incomplete resource management that can lead to memory corruption and system instability. Unlike its counterpart function airoha_qdma_cleanup_rx_queue which properly handles descriptor reset operations, the transmit queue cleanup routine fails to perform essential housekeeping tasks necessary for proper hardware state synchronization.
The technical implementation flaw stems from the asymmetric handling of cleanup operations between receive and transmit queue management within the airoha wireless driver framework. When the transmit queue cleanup function executes, it neglects to reset the DMA TX descriptors to their initial state, leaving stale data in memory locations that should be cleared for subsequent operations. Additionally, the critical step of synchronizing the TX_DMA_IDX register with TX_CPU_IDX is omitted, creating a mismatch between the hardware's perceived queue state and the actual software-managed queue status. This discrepancy can result in transmit ring management errors where the network interface believes there are pending transactions when none exist, or conversely, fails to recognize available slots for new transmissions.
The operational impact of this vulnerability extends beyond simple resource leak scenarios to encompass potential system crashes, data corruption, and network connectivity disruptions. When the transmit queue cleanup fails to properly reset descriptor states, subsequent transmission operations may encounter corrupted data structures that can trigger kernel panic conditions or cause the wireless interface to become unresponsive. The failure to synchronize index registers creates a state inconsistency that can manifest as buffer overflows or underflows in the QDMA ring management system. Network administrators may observe intermittent connectivity issues, packet loss during high-throughput scenarios, or complete driver module failures that require system rebooting to resolve.
The vulnerability aligns with CWE-704 which addresses incorrect implementation of security features and CWE-682 which covers computation with incorrect operands. From an attack perspective, this weakness could potentially be exploited by malicious actors to cause denial-of-service conditions against systems running affected wireless network drivers. The ATT&CK framework categorizes this under T1499.004 for Network Denial of Service and T1566.002 for Pre-Attack Reconnaissance activities that could lead to more sophisticated exploitation attempts. The issue demonstrates poor defensive programming practices where similar functions are not maintained with consistent implementation patterns, creating opportunities for subtle but impactful errors in kernel-level networking components.
Mitigation strategies should focus on ensuring complete descriptor reset operations and proper index synchronization during cleanup routines. System administrators should apply the relevant kernel security patches that implement the missing bits in the airoha_qdma_cleanup_tx_queue function. The fix requires resetting DMA TX descriptors to their initial state similar to the existing RX queue cleanup implementation, followed by proper synchronization of TX_DMA_IDX with TX_CPU_IDX registers. Additionally, comprehensive testing should validate that no other similar inconsistencies exist in related QDMA management functions and that all cleanup operations maintain proper synchronization between software-managed and hardware-managed queue states. Regular kernel updates and security monitoring are essential to prevent exploitation of such timing-sensitive resource management vulnerabilities in network driver implementations.