CVE-2026-19574
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BaseFortify

Publication date: 2026-10-09

Last updated on: 2026-10-09

Assigner: Zephyr Project

Description
The ARM64 MMU back-end allocated address space identifiers (ASIDs) for memory domains with a bare round-robin counter in arch_mem_domain_init() (arch/arm64/core/mmu.c). VM_ASID_BITS is 8, so only 255 ASIDs exist; once the counter wrapped, arch_mem_domain_init() could hand an ASID to a new domain while a still-live domain held the same one. Domain-private mappings are installed non-global (MT_NG), so the ASID is the only tag separating one domain's cached translations from another's in the TLB. The context-switch path in z_arm64_swap_ptables() only flushes the TLB when the outgoing and incoming domains carry the same ASID, which does not cover a duplicate reached through a third domain: for domains A and C sharing an ASID and an unrelated domain B, the schedule A -> B -> C never takes the flush branch, so the ASID-tagged entries A populated remain resident while C runs. Under SMP two live domains sharing an ASID can additionally be resident on two CPUs at once, which the architecture does not allow for distinct translation-table sets. Triggering the wrap requires a CONFIG_USERSPACE application on ARM64 that creates more than 255 memory domains over its lifetime; k_mem_domain_init() and k_mem_domain_deinit() are supervisor-only APIs and are not exposed as syscalls, so an unprivileged thread cannot drive the counter directly. Once two live domains alias, however, a user-mode thread in one domain can read and write memory belonging to the other domain's partitions and thread stacks with that domain's permissions, defeating the memory-domain isolation boundary. The fix scans the live domain_list before assigning an ASID, advances the round-robin counter past ASIDs already in use, and returns -ENOMEM when all are taken, so domain creation fails closed instead of silently aliasing.

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Meta Information

Published
2026-10-09
Last Modified
2026-10-09
Generated
2026-10-19
AI Q&A
2026-10-09
EPSS Evaluated
2026-10-18
NVD
CVE-2026-19574
EUVD
EUVD-2026-95528

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
zephyrproject zephyr 3.3.0

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-284 The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.

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Executive Summary

This vulnerability affects the Zephyr RTOS on ARM64 systems due to a flaw in the MMU's Address Space Identifier (ASID) allocation. The system uses a round-robin counter to assign ASIDs to memory domains, which wraps after 255 assignments. This can lead to ASID reuse while a domain is still active, breaking memory isolation. The TLB relies on ASIDs to separate domains, but stale entries can remain resident during context switches, allowing unauthorized access between domains.

Detection Guidance

This vulnerability affects Zephyr RTOS versions 3.3.0 to 4.4.2 on ARM64 systems. Detection requires checking the Zephyr RTOS version and ARM64 MMU configuration. Use commands like 'git log --oneline --grep="ASID"' or 'grep -r "CONFIG_USERSPACE" .config' in the Zephyr project directory to identify affected configurations.

Impact Analysis

An attacker could exploit this to bypass memory isolation, allowing a user-mode thread in one domain to read or write memory belonging to another domain. This could lead to data leaks, privilege escalation, or system compromise. Exploitation requires creating over 255 memory domains, which is limited to supervisor applications, but once domains alias, the attack becomes possible.

Compliance Impact

This vulnerability could violate data protection requirements by enabling unauthorized access to sensitive memory regions. GDPR and HIPAA mandate strict data isolation and protection; a breach of memory isolation could result in non-compliance, leading to legal penalties or data breaches.

Mitigation Strategies

Upgrade Zephyr RTOS to version 4.5.0 or later to apply the fix. If upgrading is not immediately possible, disable CONFIG_USERSPACE in the kernel configuration to prevent memory domain creation. Ensure no CONFIG_USERSPACE applications create more than 255 memory domains.

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