What’s Vulnerable › Vulnerabilities

CVE-2026-63875: arm64: tlb: Flush walk cache when unsharing PMD tables

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-19 · updated 2026-10-30
• Weakness: CWE-670

Description

In the Linux kernel, the following vulnerability has been resolved: arm64: tlb: Flush walk cache when unsharing PMD tables When huge_pmd_unshare() is called to unshare a PMD table, the tlb_unshare_pmd_ptdesc() function sets tlb->unshared_tables=true but the aarch64 tlb_flush() only checked tlb->freed_tables to determine whether to use TLBF_NONE (vae1is, invalidates walk cache) or TLBF_NOWALKCACHE (vale1is, leaf-only). This caused the stale PMD page table entry to remain in the walk cache after unshare, potentially leading to incorrect page table walks. Fix by including unshared_tables in the check, so that when unsharing tables, TLBF_NONE is used and the walk cache is properly invalidated. Here is the detailed distinction between vae1is and vale1is: | Instruction Combination | Actual Invalidation Scope | | ------------------------ | --------------------------------------------------| | `VAE1IS` + TTL=`0` | All entries at all levels (full invalidation) | | `VAE1IS` + TTL=`2` (L2) | Non-leaf at Level 0/1 + leaf at Level 2 | | `VALE1IS` + TTL=`0` | Leaf entries at all levels (non-leaf not cleared) | | `VALE1IS` + TTL=`2` (L2) | Leaf entry at Level 2 only |

Affected products

• Linux kernel: from 5.10.253 before 5.10.259; from 5.15.203 before 5.15.210; from 6.1.167 before 6.1.176; from 6.6.127 before 6.6.143; from 6.12.74 before 6.12.93; from 6.18.13 before 6.18.35 — fixed in 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.93, 6.18.35
• Linux kernel: from 5.10.253 before 5.10.259; from 5.15.203 before 5.15.210; from 6.1.167 before 6.1.176; from 6.6.127 before 6.6.143; from 6.12.74 before 6.12.93; from 6.18.13 before 6.18.35 — fixed in 5.10.259, 5.15.210, 6.1.176, 6.12.93, 6.18.35, 6.6.143

How to fix

Upgrade to a fixed version: Linux kernel 5.10.259, 5.15.210, 6.1.176, 6.6.143; Linux kernel 5.10.259, 5.15.210, 6.1.176, 6.12.93. Check the vendor advisory for mitigations.

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
• https://git.kernel.org/stable/c/d766a49d9b55705c4737cd8bb5d3faa2d31330fd
• https://git.kernel.org/stable/c/dced308d7d6a0de1c09d2058f38f1aaaf5cbb914
• https://git.kernel.org/stable/c/fe93e907b1af03cc229a80aa64a570a103d2b279

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