{"id":"CVE-2026-19574","summary":"ARM64 MMU can assign an in-use ASID to a new memory domain, breaking user-mode memory isolation","details":"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.\n\nThe 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 -\u003e B -\u003e 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.\n\nTriggering 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.\n\nThe 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.","aliases":["GHSA-923h-8c2j-pcm5"],"modified":"2026-10-11T07:04:33.326704991Z","published":"2026-10-09T07:16:43.058Z","database_specific":{"cna_assigner":"zephyr","cwe_ids":["CWE-284"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/19xxx/CVE-2026-19574.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/19xxx/CVE-2026-19574.json"},{"type":"ADVISORY","url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-923h-8c2j-pcm5"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-19574"},{"type":"FIX","url":"https://github.com/zephyrproject-rtos/zephyr/commit/805054b8ed89dd5441fbca36b3cd3be7e4fb4100"},{"type":"PACKAGE","url":"https://github.com/zephyrproject-rtos/zephyr"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/zephyrproject-rtos/zephyr","events":[{"introduced":"07c6af3b8c35c1e49186578ca61a25c76e2fb308"},{"fixed":"805054b8ed89dd5441fbca36b3cd3be7e4fb4100"}],"database_specific":{"source":["AFFECTED_FIELD","REFERENCES"],"extracted_events":[{"introduced":"3.3.0"},{"last_affected":"4.4.2"}]}}],"versions":["v4.4.0","v4.4.0-rc3","v4.4.0-rc2","v4.4.0-rc1","v4.3.0","v4.3.0-rc3","v4.3.0-rc2","v4.3.0-rc1","v4.2.0","v4.2.0-rc3","v4.2.0-rc2","v4.2.0-rc1","v4.1.0","v4.1.0-rc3","v4.1.0-rc2","v4.1.0-rc1","v4.0.0","v4.0.0-rc3","v4.0.0-rc2","v4.0.0-rc1","v3.7.0","v3.7.0-rc3","v3.7.0-rc2","v3.7.0-rc1","v3.6.0","v3.6.0-rc3","v3.6.0-rc2","v3.6.0-rc1","zephyr-v3.5.0","v3.5.0","v3.5.0-rc3","v3.5.0-rc2","v3.5.0-rc1","zephyr-v3.4.0","v3.4.0","v3.4.0-rc3","v3.4.0-rc2","v3.4.0-rc1","zephyr-v3.3.0","v3.3.0"],"database_specific":{"vanir_signatures":[{"source":"https://github.com/zephyrproject-rtos/zephyr/commit/805054b8ed89dd5441fbca36b3cd3be7e4fb4100","target":{"file":"arch/arm64/core/mmu.c","function":"arch_mem_domain_init"},"deprecated":false,"digest":{"function_hash":"26509871475832955063183339478441626532","length":629},"id":"CVE-2026-19574-4978a5a1","signature_type":"Function","signature_version":"v1"},{"target":{"file":"arch/arm64/core/mmu.c"},"deprecated":false,"digest":{"threshold":0.9,"line_hashes":["321701588271132913974739325278821316617","253599544819433668365164158925573089548","165763363246026877931405403569659499081","68934918369697023521333026559732607503","271043525200650575351772388090156153061","110610318632424932358458797701532310742","16378318233632396310115711218310718184"]},"id":"CVE-2026-19574-75d844d0","signature_type":"Line","signature_version":"v1","source":"https://github.com/zephyrproject-rtos/zephyr/commit/805054b8ed89dd5441fbca36b3cd3be7e4fb4100"}],"vanir_signatures_modified":"2026-10-11T07:04:33Z","source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-19574.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}