CVE-2026-89872 in Linux
Summary
by MITRE • 09/16/2026
In the Linux kernel, the following vulnerability has been resolved:
media: v4l2-fwnode: Fix fwnode leak in v4l2_fwnode_parse_link
In v4l2_fwnode_parse_link(), the remote endpoint fwnode reference is acquired using fwnode_graph_get_remote_endpoint(). This reference is properly released in the error paths, but it is leaked on the success path.
Add the missing fwnode_handle_put() before returning 0 to prevent the reference leak.
[Sakari Ailus: Fix subject prefix and coding style a little.]
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Analysis
by VulDB Data Team • 09/16/2026
The vulnerability identified within the Linux kernel media subsystem specifically affects the v4l2-fwnode driver component, manifesting as a resource management error in the function v4l2_fwnode_parse_link. This function is responsible for parsing firmware node links that define connections between hardware components and their drivers. During this process, the code invokes fwnode_graph_get_remote_endpoint to acquire a reference count on the remote endpoint's firmware node structure. While the implementation correctly handles resource cleanup by releasing this reference in various error paths where execution deviates from the normal flow, it fails to perform the corresponding release operation when the function completes successfully and returns zero. This oversight results in a persistent memory leak that accumulates with each successful invocation of the link parsing routine.
From a technical perspective, this flaw represents an improper resource deallocation mechanism inherent to kernel programming where reference counting is critical for maintaining system stability. The failure to call fwnode_handle_put before returning indicates a gap in the lifecycle management of firmware node objects. In Linux kernel development, every acquisition of a handle or pointer via functions that increment reference counts must be matched by a corresponding release function when the object is no longer needed. By omitting this step on the success path, the system retains an unnecessary hold on memory and potentially other associated resources tied to the firmware node structure. Over time, particularly in systems with complex media topologies or those undergoing frequent reconfiguration of hardware links, these unreleased references can lead to significant resource exhaustion.
The operational impact of this vulnerability is primarily characterized by gradual degradation of system performance due to increasing memory consumption. Although a single instance may seem negligible, the cumulative effect of repeated leaks during normal operation can contribute to overall memory pressure on the host system. In worst-case scenarios involving long-running services or devices with dynamic media graph configurations, such as mobile phones or embedded multimedia systems, this could potentially lead to out-of-memory conditions if other leak sources are also present. While it does not directly allow for arbitrary code execution or privilege escalation in its current form, resource exhaustion vulnerabilities can sometimes be leveraged indirectly to cause denial of service by exhausting available kernel memory pools required for critical operations.
This issue aligns with Common Weakness Enumeration category CWE-401 which describes missing release of memory after effective allocation. It also relates to the broader concept of improper cleanup procedures that are often found in complex driver codebases where error handling paths are meticulously crafted but success path finalization is overlooked during development or refactoring cycles. The fix involves inserting a single call to fwnode_handle_put immediately before the return statement for successful execution, ensuring symmetry between acquisition and release operations regardless of the outcome branch taken by the function logic.
Mitigation strategies focus on applying the upstream kernel patch that corrects this specific reference counting imbalance. System administrators should ensure their Linux kernels are updated to versions where this fix has been integrated into the mainline or stable branches. For developers maintaining custom builds, code review processes must emphasize strict adherence to resource management patterns, particularly verifying that every get operation is paired with a put operation across all control flow paths including success returns. Automated static analysis tools configured to detect reference count mismatches can also help identify similar issues in other parts of the media subsystem or related kernel drivers before they reach production environments.