{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-63875", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2026-63875" ], "published": "2026-07-19T14:56:29Z", "summary": "arm64: tlb: Flush walk cache when unsharing PMD tables", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\narm64: tlb: Flush walk cache when unsharing PMD tables\n\nWhen huge_pmd_unshare() is called to unshare a PMD table, the\ntlb_unshare_pmd_ptdesc() function sets tlb->unshared_tables=true\nbut the aarch64 tlb_flush() only checked tlb->freed_tables to\ndetermine whether to use TLBF_NONE (vae1is, invalidates walk\ncache) or TLBF_NOWALKCACHE (vale1is, leaf-only).\n\nThis caused the stale PMD page table entry to remain in the walk cache\nafter unshare, potentially leading to incorrect page table walks.\n\nFix by including unshared_tables in the check, so that when\nunsharing tables, TLBF_NONE is used and the walk cache is properly\ninvalidated.\n\nHere is the detailed distinction between vae1is and vale1is:\n\n| Instruction Combination | Actual Invalidation Scope |\n| ------------------------ | --------------------------------------------------|\n| `VAE1IS` + TTL=`0` | All entries at all levels (full invalidation) |\n| `VAE1IS` + TTL=`2` (L2) | Non-leaf at Level 0/1 + leaf at Level 2 |\n| `VALE1IS` + TTL=`0` | Leaf entries at all levels (non-leaf not cleared) |\n| `VALE1IS` + TTL=`2` (L2) | Leaf entry at Level 2 only |", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.12.75-1+rpt1~bookworm", "1:6.12.87-1+rpt1~bookworm" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.12.75+rpt-rpi-2712", "binary_version": "1:6.12.75-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.75+rpt-rpi-v8", "binary_version": "1:6.12.75-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.75+rpt-rpi-v8-rt", "binary_version": "1:6.12.75-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-2712", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-v8", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-v8-rt", "binary_version": "1:6.12.87-1+rpt1~bookworm" } ] }, "database_specific": { "per_version": { "1:6.12.75-1+rpt1~bookworm": { "linux_commit": "89050b1059997d38d55462b323b099a6436dc10d", "upstream_version": "6.12.75", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.12.93" }, "1:6.12.87-1+rpt1~bookworm": { "linux_commit": "ae4d75fb36deba0fe1a986d9bfae65755e082dd0", "upstream_version": "6.12.87", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.12.93" } } } }, { "package": { "ecosystem": "Raspberry Pi OS:13", "name": "linux" }, "versions": [ "1:6.12.75-1+rpt1", "1:6.18.29-1+rpt1", "1:6.18.33-1+rpt1", "1:6.18.34-1+rpt1" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.12.75+rpt-rpi-2712", "binary_version": "1:6.12.75-1+rpt1" }, { "binary_name": "linux-image-6.12.75+rpt-rpi-v8", "binary_version": "1:6.12.75-1+rpt1" }, { "binary_name": "linux-image-6.12.75+rpt-rpi-v8-rt", "binary_version": "1:6.12.75-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-2712", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v8", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v8-rt", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-2712", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v8", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v8-rt", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-2712", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v8", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v8-rt", "binary_version": "1:6.18.34-1+rpt1" } ] }, "database_specific": { "per_version": { "1:6.12.75-1+rpt1": { "linux_commit": "89050b1059997d38d55462b323b099a6436dc10d", "upstream_version": "6.12.75", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.12.93" }, "1:6.18.29-1+rpt1": { "linux_commit": "66318c5b5cd8145a662303af12ed39ac07eb27cc", "upstream_version": "6.18.29", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.35" }, "1:6.18.33-1+rpt1": { "linux_commit": "95b85bebbedcaedfa7ca79116ed38b7376fba412", "upstream_version": "6.18.33", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.35" }, "1:6.18.34-1+rpt1": { "linux_commit": "c8c7494100e99ee05b11aaa4f0588a223a63d1af", "upstream_version": "6.18.34", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.35" } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-63875" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/dced308d7d6a0de1c09d2058f38f1aaaf5cbb914" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/47490bbb05c8c0e09cc3cfd237d8934ffc340583" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/0199c9d57861f17b556b6cba1f765c7cce79745b" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/d766a49d9b55705c4737cd8bb5d3faa2d31330fd" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/8ca7284da0e67b3e71d90ec17f08286774245ad9" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/fe93e907b1af03cc229a80aa64a570a103d2b279" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/48125cd9c55cbe297b59fd1f9bda48b0960bd181" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/c2ff4764e03e7a8d758352f4aceb8fe1be6ac971" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-05T13:16:28Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.8, "cvss_v3_severity": "High", "scenario": "AV:L - The vulnerable `tlb_flush()` path is only reached through local memory-management syscalls (mmap/munmap/mprotect/mremap/fork) operating on hugetlb VMAs, not through any network-facing kernel service.\nAC:L - An attacker fully controls the trigger sequence\u2014creating shared hugetlbfs mappings (\u22651GB PUD-aligned), forking to establish shared PMD tables, and concurrently unmapping/mprotecting/mremapping to force `huge_pmd_unshare()`\u2014with no conditions outside their control.\nPR:L - Exploitation requires only an unprivileged local user capable of mapping shared hugetlb pages via hugetlbfs or SHM_HUGETLB, which is commonly available on arm64 database and container hosts with pre-reserved huge pages.\nUI:N - No victim interaction is required; the attacker sets up and triggers the stale walk-cache condition entirely within processes they control.\nS:U - Impact is confined to kernel memory-management within the same security authority (incorrect page-table walks and cross-mapping leakage within the kernel), not a VM escape or cross-authority boundary break.\nC:H - Stale non-leaf walk-cache entries after `pud_clear()` can cause incorrect page-table walks, enabling reads of memory that should be unmapped or mapped to different physical pages, constituting an arbitrary memory read primitive.\nI:H - Incorrect translations from stale PMD walk-cache entries can direct stores to unintended physical pages, and freed/reused page-table pages reached via stale cache entries provide a write/corruption primitive exploitable for control-flow hijacking.\nA:H - Stale walk-cache pointers to cleared or freed page-table structures can cause kernel faults, oops, or panics during page walks or concurrent GUP-fast access on the affected address space." } } }