CVE-2025-71071 in Linux
Summary
by MITRE • 01/13/2026
In the Linux kernel, the following vulnerability has been resolved:
iommu/mediatek: fix use-after-free on probe deferral
The driver is dropping the references taken to the larb devices during probe after successful lookup as well as on errors. This can potentially lead to a use-after-free in case a larb device has not yet been bound to its driver so that the iommu driver probe defers.
Fix this by keeping the references as expected while the iommu driver is bound.
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Analysis
by VulDB Data Team • 03/31/2026
The vulnerability CVE-2025-71071 represents a critical use-after-free condition within the Linux kernel's IOMMU subsystem, specifically affecting the Mediatek IOMMU driver implementation. This flaw manifests in the driver's handling of device references during the probe phase, creating a scenario where memory corruption can occur when device binding is deferred. The issue stems from improper reference management during device initialization, where the driver prematurely releases references to larb (local arbiter) devices that may not have completed their binding process.
The technical root cause lies in the driver's logic for managing device references during probe deferral scenarios. When the IOMMU driver attempts to lookup and bind to larb devices, it drops references that were initially acquired for device access. However, this behavior becomes problematic when probe deferral occurs, meaning the larb device has not yet been successfully bound to its driver. Under these conditions, the driver releases references that are still required, leading to a situation where freed memory may be accessed subsequently during the deferral process.
This vulnerability directly maps to CWE-416, which describes the use of freed memory condition, and can be categorized under the broader ATT&CK technique T1068 for local privilege escalation through kernel exploitation. The flaw demonstrates a classic race condition in device driver management where reference counting logic fails to account for probe deferral states, creating a window where memory objects are prematurely deallocated while still being referenced by the driver's internal state management.
The operational impact of this vulnerability extends beyond simple memory corruption, potentially enabling attackers to achieve privilege escalation or system instability. When the IOMMU driver encounters a deferral scenario, the premature release of device references creates opportunities for memory layout manipulation and arbitrary code execution. The vulnerability is particularly concerning in embedded systems and mobile devices that utilize Mediatek SoCs, where IOMMU functionality is critical for memory protection and security boundaries. Attackers could exploit this condition to gain elevated privileges within the kernel space, potentially compromising the entire system's memory protection mechanisms.
Mitigation strategies for CVE-2025-71071 require immediate kernel updates from vendors to implement the proper reference management fix. The resolution involves maintaining device references throughout the binding process until the driver has successfully completed its initialization sequence. System administrators should prioritize patching affected kernels, particularly those running on Mediatek-based platforms where IOMMU functionality is actively utilized. Additionally, monitoring for probe deferral patterns and implementing proper reference counting mechanisms can help detect similar vulnerabilities in other driver implementations. The fix aligns with security best practices for kernel driver development and emphasizes the importance of proper resource management in concurrent system environments. Organizations should also consider implementing runtime protections and kernel hardening measures to reduce the attack surface and prevent exploitation of similar reference counting vulnerabilities in the broader kernel ecosystem.