{"id":"CVE-2026-63875","title":"arm64: tlb: Flush walk cache when unsharing PMD tables","summary":"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->unshar…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 6495204f8219a57859669d618b25d06176d5a872 < dced308d7d6a0de1c09d2058f38f1aaaf5cbb914","Linux >= ce4cf24761467756462c0e1dbe4a5e9c9eb520fc < 47490bbb05c8c0e09cc3cfd237d8934ffc340583","Linux >= daa6707b71a2da23a82979fa21f788aeb706f1a2 < 0199c9d57861f17b556b6cba1f765c7cce79745b","Linux >= ff37dd18ce7739a26aab0cc2d31006a45e6bde63 < d766a49d9b55705c4737cd8bb5d3faa2d31330fd","Linux >= da06bb0ca45b1ca6f1ab55023e34e61a520337f3 < 8ca7284da0e67b3e71d90ec17f08286774245ad9","Linux >= 9b671f6f432be07c0ddd66e437d6d0e0db684f83 < fe93e907b1af03cc229a80aa64a570a103d2b279","Linux >= 8ce720d5bd91e9dc16db3604aa4b1bf76770a9a1 < 48125cd9c55cbe297b59fd1f9bda48b0960bd181","Linux >= 8ce720d5bd91e9dc16db3604aa4b1bf76770a9a1 < c2ff4764e03e7a8d758352f4aceb8fe1be6ac971","Linux >= 5.10.253 < 5.10.259","Linux >= 5.15.203 < 5.15.210","Linux >= 6.1.167 < 6.1.176","Linux >= 6.6.127 < 6.6.143","Linux >= 6.12.74 < 6.12.93","Linux >= 6.18.13 < 6.18.35","Linux 6.19"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T15:32:42.432974Z"},"published":"2026-07-19","updated":"2026-10-16","sourceUpdated":"2026-10-16T15:42:09.318Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-63875","references":[{"url":"https://git.kernel.org/stable/c/dced308d7d6a0de1c09d2058f38f1aaaf5cbb914"},{"url":"https://git.kernel.org/stable/c/47490bbb05c8c0e09cc3cfd237d8934ffc340583"},{"url":"https://git.kernel.org/stable/c/0199c9d57861f17b556b6cba1f765c7cce79745b"},{"url":"https://git.kernel.org/stable/c/d766a49d9b55705c4737cd8bb5d3faa2d31330fd"},{"url":"https://git.kernel.org/stable/c/8ca7284da0e67b3e71d90ec17f08286774245ad9"},{"url":"https://git.kernel.org/stable/c/fe93e907b1af03cc229a80aa64a570a103d2b279"},{"url":"https://git.kernel.org/stable/c/48125cd9c55cbe297b59fd1f9bda48b0960bd181"},{"url":"https://git.kernel.org/stable/c/c2ff4764e03e7a8d758352f4aceb8fe1be6ac971"}],"tags":["cve.org"],"epss":0.00176,"epssPercentile":0.0666,"ingestedAt":"2026-10-16T17:24:46.771Z","slug":"CVE-2026-63875","body":"## Overview\n\nIn 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                        |\n\n## Affected\n\n- `Linux >= 6495204f8219a57859669d618b25d06176d5a872 < dced308d7d6a0de1c09d2058f38f1aaaf5cbb914`\n- `Linux >= ce4cf24761467756462c0e1dbe4a5e9c9eb520fc < 47490bbb05c8c0e09cc3cfd237d8934ffc340583`\n- `Linux >= daa6707b71a2da23a82979fa21f788aeb706f1a2 < 0199c9d57861f17b556b6cba1f765c7cce79745b`\n- `Linux >= ff37dd18ce7739a26aab0cc2d31006a45e6bde63 < d766a49d9b55705c4737cd8bb5d3faa2d31330fd`\n- `Linux >= da06bb0ca45b1ca6f1ab55023e34e61a520337f3 < 8ca7284da0e67b3e71d90ec17f08286774245ad9`\n- `Linux >= 9b671f6f432be07c0ddd66e437d6d0e0db684f83 < fe93e907b1af03cc229a80aa64a570a103d2b279`\n- `Linux >= 8ce720d5bd91e9dc16db3604aa4b1bf76770a9a1 < 48125cd9c55cbe297b59fd1f9bda48b0960bd181`\n- `Linux >= 8ce720d5bd91e9dc16db3604aa4b1bf76770a9a1 < c2ff4764e03e7a8d758352f4aceb8fe1be6ac971`\n- `Linux >= 5.10.253 < 5.10.259`\n- `Linux >= 5.15.203 < 5.15.210`\n- `Linux >= 6.1.167 < 6.1.176`\n- `Linux >= 6.6.127 < 6.6.143`\n- `Linux >= 6.12.74 < 6.12.93`\n- `Linux >= 6.18.13 < 6.18.35`\n- `Linux 6.19`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}