CVE-2026-10669 Xtensa MPU `arch_buffer_validate()` integer-overflow lets a user thread bypass syscall pointer validation
An integer overflow in Xtensa MPU validation allows unprivileged threads to bypass memory checks, leading to kernel memory disclosure and privilege escalation.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-10669?
CVE-2026-10669 is a high-severity vulnerability in Zephyrproject Zephyr, published on 14 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
On Xtensa SoCs built with CONFIG_XTENSA_MPU and CONFIG_USERSPACE, arch_buffer_validate() in arch/xtensa/core/mpu.c — the architecture hook that verifies a user-mode-supplied buffer is accessible to the calling user thread with the requested permission — defaulted its return value to 0 (access permitted) and only set a denial result inside its per-MPU-region probe loop. When the rounded extent of the buffer wraps the 32-bit address space (size + alignment offset near SIZE_MAX, or ROUND_UP(size + offset) overflowing to 0), the loop executes zero iterations and the function returns 0 = permitted without probing any MPU region.
The syscall-layer pre-checks (K_SYSCALL_MEMORY_SIZE_CHECK / Z_DETECT_POINTER_OVERFLOW) only catch a raw addr+size wrap and do not cover the ROUND_UP-induced wrap, and the string path (arch_user_string_nlen -> arch_buffer_validate) has no syscall-layer guard at all.
An unprivileged user-mode thread can therefore pass a crafted (addr, size) to any syscall that validates user buffers via k_usermode_from_copy/to_copy or k_usermode_string_copy and have validation succeed for memory it must not access; the kernel then reads from (disclosure) or, with write=1, writes to (corruption) attacker-chosen kernel or other-partition memory on the thread's behalf, enabling information disclosure, memory corruption, privilege escalation, and denial of service.
Affected from v3.7.0 (when Xtensa MPU userspace support was added) through v4.4.0. The fix changes the default to -EINVAL (deny by default), adds an explicit size_add_overflow check, and sets the success value only after the full range has been validated.
Which versions are affected by CVE-2026-10669?
It affects 1 product.
Products include Zephyrproject Zephyr.
How do I fix CVE-2026-10669?
No fix has been published for CVE-2026-10669 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-10669 being exploited?
There is no known exploitation of CVE-2026-10669 in the wild and no public exploit code.
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Sources
Also known as GHSA-4r4p-gh69-v6w4.