CVE-2026-64234 in Linux
Summary
by MITRE • 07/24/2026
In the Linux kernel, the following vulnerability has been resolved:
tty: serial: pch_uart: add check for dma_alloc_coherent()
Add a check for dma_alloc_coherent() failure to prevent a potential NULL pointer dereference in dma_handle_rx(). Properly release DMA channels and the PCI device reference using a goto ladder if the allocation fails.
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Analysis
by VulDB Data Team • 07/24/2026
The vulnerability identified in the Linux kernel's pch_uart driver represents a critical null pointer dereference issue that could lead to system instability or denial of service conditions. This flaw exists within the serial communication subsystem specifically affecting platforms utilizing the pch_uart driver for UART operations. The root cause stems from inadequate error handling during DMA memory allocation processes, where the driver fails to properly validate the success of dma_alloc_coherent() calls before proceeding with subsequent operations.
The technical implementation flaw manifests when the driver attempts to allocate coherent DMA memory for receive operations but does not verify whether the allocation succeeds. When dma_alloc_coherent() returns a NULL pointer due to insufficient memory or hardware limitations, the subsequent dma_handle_rx() function proceeds without proper checks, leading to a direct dereference of the null pointer. This condition creates an immediate kernel panic or system crash, as the operating system cannot process a memory access to a null address. The vulnerability aligns with CWE-476 which specifically addresses null pointer dereference issues in software implementations.
The operational impact of this vulnerability extends beyond simple system crashes to encompass potential security implications within embedded systems and server environments where reliable serial communication is critical. Attackers could exploit this weakness to cause persistent denial of service conditions, particularly in environments where the pch_uart driver is actively used for console output or communication with peripheral devices. The flaw becomes especially concerning in industrial control systems, embedded IoT devices, and server platforms that rely on consistent UART functionality for system monitoring and management operations.
Mitigation strategies for this vulnerability require implementing robust error handling mechanisms within the driver's initialization sequence. The recommended approach involves utilizing a goto ladder pattern to ensure proper cleanup of DMA channels and PCI device references when allocation failures occur. This defensive programming technique prevents resource leaks while maintaining system stability through controlled error recovery paths. Additionally, system administrators should prioritize kernel updates to incorporate the patched version that includes the mandatory dma_alloc_coherent() validation checks. The solution also aligns with ATT&CK technique T1499 which addresses the exploitation of resource exhaustion vulnerabilities in operating system components.
Security practitioners should monitor for potential indirect exploitation vectors where this vulnerability might be combined with other memory corruption issues to escalate privileges or gain unauthorized access to system resources. The fix demonstrates proper defensive programming practices that should be adopted across similar kernel drivers handling DMA operations, ensuring consistent error handling patterns throughout the kernel's device driver framework. Regular security auditing of kernel subsystems should include verification of DMA allocation error handling to prevent similar vulnerabilities from emerging in other device drivers within the Linux kernel ecosystem.