{"id":"UBUNTU-CVE-2026-79979","details":"The arm64 MMU backend invalidates a single virtual address from the TLB with invalidate_tlb_page() in arch/arm64/core/mmu.c, which issued TLBI VAE1{IS} with an operand of virt \u003e\u003e 12. That operand encodes the ASID in bits [63:48], so the invalidation only ever matched ASID 0 (the kernel page tables) and global entries. Memory domains, however, are allocated ASIDs starting at 1 in arch_mem_domain_init(), and every domain-private leaf created by private_map() is mapped with MT_NG, i.e. non-global. A domain's cached translation therefore survived the invalidation. All callers of invalidate_tlb_page() are demand-paging paths. When the eviction algorithm reclaims a frame, page_frame_prepare_locked() in kernel/mmu.c calls arch_mem_page_out(), which marks the kernel leaf invalid, propagates the invalid descriptor into every domain via sync_domains(), and then flushes only ASID 0. do_page_fault() immediately reuses the very same page frame for the incoming mapping through arch_mem_page_in(). A user thread that had already touched the evicted page — a k_mem_partition added with arch_mem_domain_partition_add(), or its own stack mapped by map_thread_stack() — retains a valid EL0 read/write translation to that physical frame under its own ASID. Unprivileged code running in a user thread can drive memory pressure to force eviction and then keep accessing the stale address, obtaining read and write access to whatever the kernel subsequently placed in that frame: supervisor data, another memory domain's partition, or another thread's stack. This defeats the isolation that CONFIG_USERSPACE is meant to enforce, allowing information disclosure and memory corruption up to full compromise of the system. The fix switches the implementation to TLBI VAAE1{IS}, which matches every ASID and both global and non-global entries, so no domain-tagged translation survives a page out, dirty-bit update or access-flag clear. Exploitation requires an arm64 build with both CONFIG_USERSPACE and CONFIG_DEMAND_PAGING enabled, an active backing store, and at least one demand-paged page that is also privately mapped into a user memory domain. The same commit additionally stops globalize_table() from stripping EL0 permission and non-global attributes off domain-private leaves during paging synchronization, which previously caused user threads to lose access to their own partitions and stacks.","modified":"2026-10-27T04:17:56.879866045Z","published":"2026-10-26T00:00:00Z","upstream":["CVE-2026-79979"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-79979"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-79979"},{"type":"REPORT","url":"https://github.com/zephyrproject-rtos/zephyr/commit/d732e9f808f16911d06769b3f756246f3528669f"},{"type":"REPORT","url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-6pqm-hfxf-48qv"}],"affected":[{"package":{"name":"zephyr","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/zephyr?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.1.2-1","3.1.2-1build1"],"ecosystem_specific":{"binaries":[{"binary_version":"3.1.2-1build1","binary_name":"libzephyr4"},{"binary_version":"3.1.2-1build1","binary_name":"libzephyr4-krb5"},{"binary_name":"zephyr-clients","binary_version":"3.1.2-1build1"},{"binary_version":"3.1.2-1build1","binary_name":"zephyr-server"},{"binary_version":"3.1.2-1build1","binary_name":"zephyr-server-krb5"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-79979.json"}},{"package":{"name":"zephyr","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/zephyr?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.1.2-1build1","3.1.2-1build2"],"ecosystem_specific":{"binaries":[{"binary_version":"3.1.2-1build2","binary_name":"libzephyr4"},{"binary_version":"3.1.2-1build2","binary_name":"libzephyr4-krb5"},{"binary_name":"zephyr-clients","binary_version":"3.1.2-1build2"},{"binary_version":"3.1.2-1build2","binary_name":"zephyr-server"},{"binary_name":"zephyr-server-krb5","binary_version":"3.1.2-1build2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-79979.json"}},{"package":{"name":"zephyr","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/zephyr?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.1.2-1build3"],"ecosystem_specific":{"binaries":[{"binary_name":"libzephyr4","binary_version":"3.1.2-1build3"},{"binary_name":"libzephyr4-krb5","binary_version":"3.1.2-1build3"},{"binary_version":"3.1.2-1build3","binary_name":"zephyr-clients"},{"binary_name":"zephyr-server","binary_version":"3.1.2-1build3"},{"binary_version":"3.1.2-1build3","binary_name":"zephyr-server-krb5"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-79979.json"}},{"package":{"name":"zephyr","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/zephyr?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.1.2-1build3"],"ecosystem_specific":{"binaries":[{"binary_name":"libzephyr4","binary_version":"3.1.2-1build3"},{"binary_name":"libzephyr4-krb5","binary_version":"3.1.2-1build3"},{"binary_name":"zephyr-clients","binary_version":"3.1.2-1build3"},{"binary_version":"3.1.2-1build3","binary_name":"zephyr-server"},{"binary_version":"3.1.2-1build3","binary_name":"zephyr-server-krb5"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-79979.json"}},{"package":{"name":"zephyr","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/zephyr?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.1.2-1.1","3.1.2-1.1build1"],"ecosystem_specific":{"binaries":[{"binary_name":"libzephyr4","binary_version":"3.1.2-1.1build1"},{"binary_name":"libzephyr4-krb5","binary_version":"3.1.2-1.1build1"},{"binary_version":"3.1.2-1.1build1","binary_name":"zephyr-clients"},{"binary_name":"zephyr-server","binary_version":"3.1.2-1.1build1"},{"binary_version":"3.1.2-1.1build1","binary_name":"zephyr-server-krb5"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-79979.json"}},{"package":{"name":"zephyr","ecosystem":"Ubuntu:26.10","purl":"pkg:deb/ubuntu/zephyr?arch=source&distro=stonking"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.1.2-4"],"ecosystem_specific":{"binaries":[{"binary_name":"libzephyr4","binary_version":"3.1.2-4"},{"binary_version":"3.1.2-4","binary_name":"libzephyr4-krb5"},{"binary_version":"3.1.2-4","binary_name":"zephyr-clients"},{"binary_name":"zephyr-server","binary_version":"3.1.2-4"},{"binary_name":"zephyr-server-krb5","binary_version":"3.1.2-4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-79979.json"}},{"package":{"name":"zephyr","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/zephyr?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.1.2-1.1buil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