CVE-2026-63997 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
ethtool: module: avoid leaking a netdev ref on module flash errors
module_flash_fw_schedule() is missing undo for setting the "in_progress" flag and taking the netdev reference. Delay taking these, the device can't disappear while we are holding rtnl_lock.
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Analysis
by VulDB Data Team • 07/19/2026
This vulnerability resides within the linux kernel's ethtool module where a potential resource leak occurs during firmware flashing operations. The issue manifests when the module_flash_fw_schedule() function fails to properly handle cleanup operations upon encountering errors during the flash process. Specifically, the function sets an "in_progress" flag and takes a netdev reference without ensuring proper undo operations if subsequent steps fail. This creates a scenario where network device references remain active even after error conditions have occurred, leading to potential memory leaks and resource exhaustion.
The technical flaw stems from improper resource management within the kernel's networking subsystem where the function fails to maintain atomicity between flag setting and reference counting operations. When errors occur during firmware flashing, the system does not properly release the netdev reference that was acquired, leaving the network device structure in a partially initialized state. This type of resource leak falls under the category of improper cleanup operations as classified by CWE-459, where resources are not properly released after use. The vulnerability specifically impacts the kernel's ability to manage network device references correctly during error handling scenarios.
The operational impact of this vulnerability extends beyond simple memory consumption issues to potentially destabilize network operations within the system. When multiple firmware flashing operations fail and accumulate unreleased netdev references, it can lead to system resource exhaustion that affects overall network functionality and system stability. The vulnerability is particularly concerning in environments where frequent firmware updates occur or where automated systems continuously attempt firmware flashing operations. Attackers could potentially exploit this weakness to cause denial of service conditions by triggering repeated error scenarios that accumulate unreleased resources.
The root cause is further exacerbated by the fact that the kernel maintains a lock-based approach using rtnl_lock for device management, yet the code does not properly account for the timing of reference acquisition relative to error handling. According to ATT&CK framework technique T1499.004, this vulnerability could be leveraged to cause resource exhaustion through improper use of system resources, while the underlying CWE-459 classification indicates poor resource management practices. The recommended mitigation involves restructuring the module_flash_fw_schedule() function to delay taking netdev references until after all error conditions have been properly validated, ensuring that any reference acquisition is paired with appropriate cleanup operations regardless of execution path. Additionally, implementing proper error handling frameworks that automatically release resources on failure conditions would address this vulnerability comprehensively.
The fix requires careful consideration of the kernel's locking mechanisms and resource management protocols to ensure that netdev references are taken only when necessary and properly released in all code paths. This approach aligns with security best practices for kernel development where resource leaks can create persistent vulnerabilities. The solution must maintain the existing functionality while ensuring proper cleanup semantics, particularly in error conditions that occur during firmware flashing operations.