{"cve":"CVE-2026-63875","nvd":{"published":"2026-07-19T16:17:04.357","modified":"2026-10-19T21:17:08.647","status":"Undergoing Analysis","description":"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                        |","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":["CWE-459"],"references":["https://git.kernel.org/stable/c/0199c9d57861f17b556b6cba1f765c7cce79745b","https://git.kernel.org/stable/c/47490bbb05c8c0e09cc3cfd237d8934ffc340583","https://git.kernel.org/stable/c/48125cd9c55cbe297b59fd1f9bda48b0960bd181","https://git.kernel.org/stable/c/8ca7284da0e67b3e71d90ec17f08286774245ad9","https://git.kernel.org/stable/c/c2ff4764e03e7a8d758352f4aceb8fe1be6ac971"],"products":[],"source":"nvd","synced_at":"2026-10-21T03:43:09.190223697+00:00"},"epss":{"cve":"CVE-2026-63875","score":0.00176,"percentile":0.07125,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}