CVE-2026-63862 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
PCI: mediatek-gen3: Prevent leaking IRQ domains when IRQ not found
In mtk_pcie_setup_irq(), the IRQ domains are allocated before the controller's IRQ is fetched. If the latter fails, the function directly returns an error, without cleaning up the allocated domains.
Hence, reverse the order so that the IRQ domains are allocated after the controller's IRQ is found.
This was flagged by Sashiko during a review of "[PATCH v6 0/7] PCI:
mediatek-gen3: add power control support".
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 07/19/2026
The vulnerability described in this CVE relates to a resource leak condition within the Linux kernel's PCI subsystem, specifically affecting the Mediatek PCIe Gen3 driver implementation. This flaw occurs during the initialization process of PCIe controller interrupts where the kernel fails to properly clean up allocated resources when subsequent operations encounter failures. The issue manifests in the mtk_pcie_setup_irq() function which demonstrates improper resource management sequence that violates fundamental principles of defensive programming and system reliability.
The technical root cause stems from a problematic execution flow where IRQ domains are allocated before verifying the availability and proper configuration of the controller's interrupt source. When the controller's IRQ retrieval operation fails, the function exits immediately with an error code while leaving previously allocated IRQ domain structures in memory without proper cleanup. This represents a classic resource leak scenario that can accumulate over time and potentially lead to system instability or denial of service conditions. The vulnerability directly maps to CWE-404, which categorizes improper resource cleanup or release as a well-known weakness in software security practices.
The operational impact of this vulnerability extends beyond simple memory consumption issues to potentially compromise system integrity and availability. In embedded systems running Linux kernels with Mediatek PCIe Gen3 controllers, repeated initialization attempts may cause progressive memory fragmentation and resource exhaustion. The flaw becomes particularly concerning in environments where PCIe devices are frequently hot-plugged or reconfigured, as each failed initialization cycle contributes to the accumulation of leaked resources. This behavior could enable an attacker to perform resource exhaustion attacks that degrade system performance or cause unexpected service interruptions.
Security implications of this vulnerability align with ATT&CK technique T1499.003, which covers resource exhaustion attacks targeting system services. The improper cleanup mechanism creates a persistent state where allocated kernel memory remains unreleased even after failed operations, providing potential attack vectors for adversaries seeking to destabilize systems through resource manipulation. Additionally, the vulnerability demonstrates poor error handling practices that could mask underlying hardware configuration issues or indicate more serious driver compatibility problems within the PCIe subsystem.
The recommended mitigation strategy involves implementing proper resource management ordering where all allocations occur only after successful validation of prerequisites. This approach ensures that if any subsequent operation fails, the system can safely unwind and release previously allocated resources without leaving dangling references or memory leaks. The fix requires modifying the mtk_pcie_setup_irq() function to reverse the allocation sequence, ensuring IRQ domains are created only after confirming the controller's interrupt source is properly available. This defensive programming approach prevents resource leakage while maintaining system stability and reliability during PCIe initialization processes.
The vulnerability highlights the importance of proper error handling in kernel space code where resource leaks can have cascading effects on system performance and security posture. Modern kernel development practices emphasize the principle of "fail fast" combined with proper cleanup mechanisms to ensure that even when operations fail, system resources remain properly managed and available for subsequent operations. This particular fix exemplifies how careful attention to execution flow and resource management sequence can prevent seemingly minor programming errors from becoming significant security or stability issues in production systems.