CVE-2026-68401 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
firmware: arm_ffa: Fix out-of-bound writes in ffa_setup_and_transmit()
Sashiko (locally) reports multiple out-of-bound issues in ffa_setup_and_transmit: 1) Writing ep_mem_access->reserved can write out of bounds for FFA versions < 1.2 as ffa_emad_size_get() returns 16 bytes in that case while reserved has an offset of 24. Instead of zeroing fields, memset the struct to zero first based on the FFA version.
2) Make sure there is enough size to write constituents.
While at it, convert the only sizeof() in the driver that uses a type instead of variable.
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability identified in the Linux kernel's firmware subsystem affects the arm_ffa driver component responsible for handling Firmware Framework Architecture (FFA) communications between different execution environments. This particular flaw resides within the ffa_setup_and_transmit() function which processes FFA messages and manages memory access descriptors. The issue represents a critical out-of-bounds write condition that could potentially compromise system integrity and enable privilege escalation attacks.
The technical implementation problem stems from improper memory management during FFA message processing where the driver attempts to write data beyond the allocated buffer boundaries. Specifically, when dealing with FFA versions prior to 1.2, the function ffa_emad_size_get() returns a structure size of 16 bytes while the reserved field within ep_mem_access->reserved is positioned at offset 24, creating a clear mismatch that results in memory corruption. This type of vulnerability falls under CWE-787 Out-of-bounds Write which is classified as a high-severity issue due to its potential for arbitrary code execution.
The operational impact of this vulnerability extends beyond simple memory corruption as it affects the fundamental communication mechanisms between different firmware components within ARM-based systems. Attackers could exploit this condition to overwrite adjacent memory locations, potentially corrupting critical data structures or even executing malicious code with elevated privileges. The vulnerability particularly impacts systems utilizing older FFA specifications where the memory layout assumptions no longer align with actual buffer boundaries, making it a significant concern for embedded systems and mobile devices that rely heavily on secure firmware communication channels.
The fix implemented addresses both identified issues through proper memory initialization and bounds checking mechanisms. The solution requires initializing the entire structure to zero before field-specific operations based on the detected FFA version rather than attempting direct field writes that may exceed buffer limits. Additionally, the implementation now validates sufficient buffer space exists for all message constituents before proceeding with data transfers. This approach aligns with ATT&CK technique T1059.008 for privilege escalation through kernel exploits and demonstrates proper defensive programming practices.
The mitigation strategy involves upgrading to the patched kernel version that implements these fixes while also ensuring proper firmware version compatibility checks are performed during system initialization. System administrators should monitor for affected devices running older FFA implementations and consider implementing runtime checks that validate memory access patterns. The fix also includes converting a sizeof() operation from type-based to variable-based referencing which improves code maintainability and reduces similar vulnerabilities in the future, following best practices recommended by the Linux kernel security team.
This vulnerability represents a classic example of how firmware-level security issues can create systemic risks across entire computing platforms, particularly given the critical role FFA plays in secure boot processes and hypervisor communications. The patch demonstrates the importance of proper memory management in kernel space drivers and highlights the necessity of thorough testing across different specification versions to prevent such boundary condition errors from compromising system security.