Preface: CVE-2025-10286: Details of this third-party CVE released by ARM, reported on October 27, 2025, with a customer notification date of July 6, 2026. Information about this vulnerability was also published in Qualcomm’s security bulletin on October 5, 2026.
Background: This article described does not refer to a general CPU L1/L2 data cache. Instead, it details a highly specialized sideband mechanism within the MMU/SMMU architecture of ARMv8/v9 processors (including Qualcomm Snapdragon platforms) designed for hardware virtualization and page table management.
Based on a microarchitectural analysis displayed on infographic and the logic within the conceptual pseudo-code, this code outlines the intended hardware defense mechanism (the enforcement check) rather than the exploit code itself.
However, if a vulnerability like CVE-2025-10286 were to be triggered or exist within this specific implementation, it would stem from subtle microarchitectural flaws or bypasses in how this logic is executed at the hardware level.
There are three primary vulnerabilities or edge cases within this pseudo-code flow that could lead to a security bypass. Here is an example.
Please note that the accompanying infographics should be consulted when understanding this concept.
•The Flow: At step 2, the hardware reads the memory (current_val), applies the mask, verifies it at step 3, and then commits the write using execute_hardware_limited_write(…, target_val).
•The Flaw: If a malicious agent running on a parallel core or via a separate DMA stream modifies the Stage-1 descriptor in memory exactly between the read check (current_val) and the eventual write, the verification becomes stale.
•The Attack: The committed target_val could overwrite the newly changed memory with an unvetted or structurally modified descriptor, bypassing Stage-2 hypervisor boundaries.
To mitigate the microarchitectural Time-of-Check to Time-of-Use (TOCTOU) race condition outlined in the infographic for CVE-2025-10286, the remedy requires hardware-level modifications or firmware/microcode updates to the CPU’s Memory Management Unit (MMU) and interconnect bus fabric.
Vulnerability details: CVE ID – CVE-2025-10286
Title: Buffer Over-read in CPU SW
Description: Third-party CVE details issued by ARM.
When the sideband cache is enabled, malicious EL1 software may be able to read or write to an arbitrary memory location which should not be accessible due to Stage-2 translation. Writes are limited to updating the Access Flag (AF) and/or dirty bit (AP[2]) fields when the memory location is interpreted as a stage 1 translation table descriptor in the endianness of the stage 1 translation regime.
Official announcement: Please refer to the link for details –
https://docs.qualcomm.com/securitybulletin/october-2026-bulletin.html