Xtensa MPU `arch_buffer_validate()` integer-overflow lets a user thread bypass syscall pointer validation

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-10669
StatePUBLISHED
Assignerzephyr
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-14 15:16:55 UTC
Updated2026-07-14 19:16:50 UTC
DescriptionOn 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.

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.001140000 probability, percentile 0.017450000 (date 2026-07-15)

Problem Types: CWE-787 | CWE-787 bounds

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNACVSS7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Zephyrproject Zephyr affected 3.7.0 4.5.0 semver Not specified

References

ReferenceSourceLinkTags
github.com/zephyrproject-rtos/zephyr/commit/3b1bdaf5482188ca110ef9a411aa... [email protected] github.com
github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-4r4p-gh69-... [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

© CVE.report 2026

Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties, implied or otherwise, with regard to this information or its use. Any use of this information is at the user's risk. It is the responsibility of user to evaluate the accuracy, completeness or usefulness of any information, opinion, advice or other content. EACH USER WILL BE SOLELY RESPONSIBLE FOR ANY consequences of his or her direct or indirect use of this web site. ALL WARRANTIES OF ANY KIND ARE EXPRESSLY DISCLAIMED. This site will NOT BE LIABLE FOR ANY DIRECT, INDIRECT or any other kind of loss.

CVE, CWE, and OVAL are registred trademarks of The MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. This site includes MITRE data granted under the following license.

Free CVE JSON API cve.report/api

CVE.report and Source URL Uptime Status status.cve.report