{"schema":"threatline.record/2","record":{"id":"CVE-2026-19574","aliases":["GHSA-923h-8c2j-pcm5"],"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 -> 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.\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.","categories":["Unclassified"],"product":"zephyr","vendor":"zephyrproject","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-19574","source_modified_at":"2026-10-09T17:56:48.909Z","fetched_at":"2026-10-23T18:48:36.087640Z","product":"zephyr","vendor":"zephyrproject","versions":[{"lessThanOrEqual":"4.4.2","status":"affected","version":"3.3.0","versionType":"semver"}],"defaultStatus":"unaffected"},{"source":"GitHub Advisory Database","source_url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-923h-8c2j-pcm5","source_modified_at":"2026-10-09T07:03:43Z","fetched_at":"2026-10-23T20:39:26.410340Z","package":{"ecosystem":"other","name":"zephyr"},"range":">= 3.3.0, <= 4.4.2"}],"fixed_versions":[{"source":"GitHub Advisory Database","source_url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-923h-8c2j-pcm5","source_modified_at":"2026-10-09T07:03:43Z","fetched_at":"2026-10-23T20:39:26.410340Z","package":{"ecosystem":"other","name":"zephyr"},"version":"4.5.0"}],"cvss":7,"severity":"High","kev":{"listed":false},"epss":{"probability":0.00097,"percentile":0.00684,"score_date":"2026-10-23"},"published_at":"2026-10-09T07:16:43.058Z","modified_at":"2026-10-09T17:56:48.909Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-19574","fetched_at":"2026-10-23T18:48:36.087640Z","source_modified_at":"2026-10-09T17:56:48.909Z"},{"source":"GitHub Advisory Database","url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-923h-8c2j-pcm5","fetched_at":"2026-10-23T20:39:26.410340Z","source_modified_at":"2026-10-09T07:03:43Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-19574","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","GitHub Advisory Database","EPSS"],"references":[{"source":"CVE List","url":"https://github.com/zephyrproject-rtos/zephyr/commit/805054b8ed89dd5441fbca36b3cd3be7e4fb4100","tags":["patch"]},{"source":"CVE List","url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-923h-8c2j-pcm5"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","ssvc":{"exploitation":"none","automatable":"no","technical_impact":"total","assessed_at":"2026-10-09T17:56:13.062546Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":null,"confidence":"unknown","reviewed":false},"change_timestamp":"2026-10-09T17:56:48.909Z","content_hash":"02219ea32a8224993a01242880d0d4b71abd1fc1ccd4ccd4071cbacae649837d"}}