CVE-2026-89944 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
ASoC: hdac_hda: Fix hlink refcount leak on component registration failure
hdac_hda_dev_probe() gets the HDA link with snd_hdac_ext_bus_link_get() before registering the ASoC component. If component registration fails, the function returns without dropping the link reference.
Always call snd_hdac_ext_bus_link_put() after the registration attempt so the reference taken during probe is balanced on both success and failure.
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Analysis
by VulDB Data Team • 09/17/2026
The vulnerability described involves a resource management flaw within the Linux kernel's Advanced Sound Architecture (ASoC) subsystem, specifically in the High Definition Audio Controller driver for HD-audio devices. The core issue resides in the hdac_hda_dev_probe function, which is responsible for initializing and registering audio components during system boot or device insertion events. During this initialization sequence, the code invokes snd_hdac_ext_bus_link_get to acquire a reference count on an HDA link object. This operation increments an internal counter that tracks active references to ensure the underlying hardware interface remains valid and accessible while in use. The subsequent step involves registering the ASoC component with the kernel's sound subsystem, which can potentially fail due to various reasons such as missing dependencies, configuration errors, or resource conflicts.
The critical technical flaw occurs when this registration process fails. In a correctly implemented reference counting scheme, every successful call to get must be balanced by a corresponding put operation to prevent memory leaks and dangling pointers. However, in the affected code path, if component registration returns an error code, the function exits immediately without invoking snd_hdac_ext_bus_link_put. This omission means that the reference count acquired at the beginning of the probe remains elevated indefinitely. Over time, as devices are probed or re-probed, this unbalanced increment leads to a cumulative leak of kernel memory and resource handles associated with the HDA link object. While individual instances might seem minor, repeated occurrences can contribute to system instability, increased memory pressure, and potentially denial-of-service conditions if other resources tied to these references are exhausted.
From a classification perspective, this vulnerability aligns with CWE-401, which describes missing release of memory after effective usage, often referred to as a resource leak or reference count imbalance. It also relates to CWE-755, improper handling of unusual or exceptional conditions, specifically the failure to clean up resources when an error path is taken. In terms of adversarial tactics, this type of flaw can be leveraged in conjunction with other vulnerabilities for denial-of-service attacks, falling under MITRE ATT&CK technique T1499, Endpoint Denial of Service, where attackers aim to degrade system performance or availability by exhausting resources. Although the primary impact here is resource exhaustion rather than direct code execution, the accumulation of leaked references can destabilize the kernel's internal state management mechanisms.
The operational impact of this vulnerability includes gradual degradation of system stability over time, particularly on systems with multiple audio devices or frequent device hot-plugging events. Administrators may observe increasing memory usage by kernel processes related to sound drivers and eventual failure of new audio components to initialize correctly due to exhausted reference slots. To mitigate this issue, the recommended action is to apply the upstream Linux kernel patch that ensures snd_hdac_ext_bus_link_put is called unconditionally after the registration attempt, regardless of whether it succeeds or fails. This guarantees that the reference count is properly decremented in all execution paths, maintaining consistency and preventing leaks. System administrators should ensure their kernels are updated to versions containing this fix, typically by updating to a recent stable release where such driver corrections have been merged into the mainline tree.