CVE-2026-90378 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
wifi: mt76: mt792x: Fix memory leak in SDIO TX path
When tx_prepare_skb() returns an error in the SDIO TX path, the skb is not freed, leading to a memory leak. This can occur when zero-length frames (such as WNM NULL frames) are dropped to prevent potential hardware TX hangs.
Fix this by properly releasing the skb with ieee80211_tx_status_ext() when tx_prepare_skb() fails.
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Analysis
by VulDB Data Team • 09/17/2026
The Linux kernel wireless subsystem, specifically within the MediaTek MT792x driver implementation for SDIO interfaces, contained a resource management flaw in its transmission path that resulted in memory leaks under specific error conditions. This vulnerability is rooted in the handling of socket buffers during packet preparation and subsequent status reporting. The core issue arises when the tx_prepare_skb function encounters an error while processing outgoing network packets. In normal operation, this function prepares the sk_buff structure for hardware transmission by mapping DMA buffers and setting up necessary metadata. However, if this preparation fails, the driver must ensure that any allocated resources associated with the buffer are properly released to prevent accumulation in system memory.
The specific scenario triggering this flaw involves zero-length frames, such as WNM NULL frames used in Wireless Network Management protocols for keep-alive or status updates. To mitigate potential hardware transmission hangs caused by these empty packets, the driver logic is designed to drop them rather than attempting full transmission preparation. When tx_prepare_skb returns an error code indicating that the frame cannot be processed further, the original implementation failed to invoke the appropriate cleanup routine. Consequently, the sk_buff structure and its associated memory allocations remained allocated in kernel space without being returned to the available pool. Over time, particularly under high network activity involving frequent management frames, this unchecked allocation leads to a gradual depletion of kernel memory resources.
From a technical classification perspective, this vulnerability aligns with CWE-401, which describes missing release of memory after effective usage. The failure to free dynamically allocated memory upon error paths is a classic example of improper resource cleanup that can degrade system stability. In the context of attack vectors and operational impact, while this specific flaw does not directly allow for remote code execution or privilege escalation, it contributes to Denial of Service conditions through resource exhaustion. An attacker capable of inducing high volumes of zero-length management frames could accelerate memory consumption, potentially leading to kernel oopses, system crashes, or significant performance degradation as the system struggles with insufficient memory availability. This behavior is consistent with patterns observed in ATT&CK technique T1496, Resource Hijacking, where an adversary consumes resources to disrupt service availability.
The resolution involves correcting the error handling logic within the SDIO transmission path by ensuring that ieee80211_tx_status_ext is called when tx_prepare_skb fails. This function properly handles the release of the sk_buff and any associated DMA mappings, thereby restoring correct resource lifecycle management. By integrating this fix, the driver ensures that all allocated buffers are freed regardless of whether they proceed to hardware transmission or are dropped due to preparation errors. This change reinforces robustness in the network stack by preventing memory leaks during edge cases involving small control frames.
To mitigate similar issues and maintain system integrity, developers should rigorously audit error paths in kernel drivers for proper resource release patterns. It is essential that every allocation has a corresponding deallocation path, including all exceptional conditions such as hardware errors or invalid input parameters. Regular static analysis tools can help identify these discrepancies before deployment. For administrators running affected systems, applying the latest kernel updates containing this patch is critical to preventing long-term memory degradation and maintaining stable wireless connectivity performance on devices utilizing MediaTek MT792x chipsets over SDIO interfaces.