{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89961", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.778Z", "datePublished": "2026-09-16T10:32:43.921Z", "dateUpdated": "2026-10-19T08:55:35.034Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:55:35.034Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\npowerpc/mm: fix wrong addr_pfn tracking in compound vmemmap population\n\nvmemmap_populate_compound_pages() uses addr_pfn to determine the PFN\noffset within a compound page and to decide whether the current vmemmap\nslot should be populated as a head page mapping or should reuse a tail\npage mapping.\n\nHowever, addr_pfn is advanced manually in parallel with addr. The loop\nitself progresses in vmemmap address space, so each PAGE_SIZE step in addr\ncovers PAGE_SIZE / sizeof(struct page) struct page slots. Since addr_pfn\nis compared against nr_pages in data-PFN units, it should advance by the\nsame number of PFNs. The existing manual increments do not match that and\ntherefore do not reliably track the PFN corresponding to the current addr.\n\nAs a result, pfn_offset can be computed from the wrong PFN and the code\ncan make the head/tail decision for the wrong compound-page position.\n\nFix this by deriving addr_pfn directly from the current vmemmap address\ninstead of carrying it as loop state." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The bug is in powerpc radix vmemmap_populate_compound_pages(), reached only through local ZONE_DEVICE hotplug (dev_dax_probe → devm_memremap_pages → arch_add_memory → sparse_add_section). It is not reachable from network protocols, Bluetooth, or USB.\nAC:L - Once device-DAX with compound vmemmap is mapped (2MB PMD on 4K kernels or 1GB PUD on 64K, the documented powerpc DAX configs), addr_pfn drifts on every loop iteration and the wrong head/tail mapping is deterministic; no race or attacker-uncontrollable layout is required.\nPR:L - Initial memremap requires administrator DAX setup, but on a provisioned persistent-memory or cloud POWER server an unprivileged local user with /dev/dax access can mmap the device and drive kernel use of the mis-aliased struct pages via faults and GUP without init-namespace CAP_SYS_ADMIN.\nUI:N - Exploitation needs no victim action; the attacker mmaps or faults the already-provisioned DAX device themselves. No mount, click, or hotplug by another user is required at exploit time.\nS:U - Impact is kernel struct-page aliasing and MM corruption inside the same host kernel security authority. It is not a KVM guest-to-host escape, IOMMU/DMA bypass, or sandbox boundary crossing.\nC:H - Wrong pfn_offset aliases distinct vmemmap pages so different DAX PFNs share struct-page backing; later memmap_init, faults, and GUP read corrupted flags, mapping, and compound-head fields, disclosing kernel memory via that metadata.\nI:H - The same aliases turn kernel writes (page init, folio mapping, refcount, compound head/tail linkage) into writes to the wrong struct pages, an exploitable kernel memory-corruption primitive that can hijack control flow rather than a bounded data modification.\nA:H - Mis-linked compound pages and aliased vmemmap cause kernel oops, BUG_ON, or panic when MM code walks folio heads, refcounts, or DAX fault handlers, fully denying availability of the affected POWER radix host." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "arch/powerpc/mm/book3s64/radix_pgtable.c" ], "versions": [ { "version": "f2b79c0d79683d552369bb9a7282c1f0226fc566", "lessThan": "b96be860673f9fbbf12cdadb0b25fc4d6d4d207f", "status": "affected", "versionType": "git" }, { "version": "f2b79c0d79683d552369bb9a7282c1f0226fc566", "lessThan": "e163c7184acf36ac20a248498f4a16016057ca01", "status": "affected", "versionType": "git" }, { "version": "f2b79c0d79683d552369bb9a7282c1f0226fc566", "lessThan": "9c914b7a0bd18834505c65f22225ce22c152b2d9", "status": "affected", "versionType": "git" }, { "version": "f2b79c0d79683d552369bb9a7282c1f0226fc566", "lessThan": "7968852a7ca3ce81477ec5b4494a28d612f35a97", "status": "affected", "versionType": "git" }, { "version": "f2b79c0d79683d552369bb9a7282c1f0226fc566", "lessThan": "89a4ae32764172468dea303eb6ae90fe6c859712", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "arch/powerpc/mm/book3s64/radix_pgtable.c" ], "versions": [ { "version": "6.6", "status": "affected" }, { "version": "0", "lessThan": "6.6", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.157", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.110", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.51", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.5", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "6.6.157" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "6.12.110" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "6.18.51" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "7.2.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/b96be860673f9fbbf12cdadb0b25fc4d6d4d207f" }, { "url": "https://git.kernel.org/stable/c/e163c7184acf36ac20a248498f4a16016057ca01" }, { "url": "https://git.kernel.org/stable/c/9c914b7a0bd18834505c65f22225ce22c152b2d9" }, { "url": "https://git.kernel.org/stable/c/7968852a7ca3ce81477ec5b4494a28d612f35a97" }, { "url": "https://git.kernel.org/stable/c/89a4ae32764172468dea303eb6ae90fe6c859712" } ], "title": "powerpc/mm: fix wrong addr_pfn tracking in compound vmemmap population", "x_generator": { "engine": "bippy-1.2.0" } } } }