# CVE-2026-98638: KVM: arm64: Validate the SVE vector length in pkvm_vcpu_init_sve()

CVE-2026-98638 is fixed in 20 products on 1 platform, first by DEBIAN-CVE-2026-98638, released October 19, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-98638
- Priority: High
- CVSS: n/a (important)
- EPSS: 0.0017
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 18, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-98638

## Description

In the Linux kernel, the following vulnerability has been resolved:  KVM: arm64: Validate the SVE vector length in pkvm_vcpu_init_sve()  pkvm_vcpu_init_sve() clamps only the upper bound of the host-provided sve_max_vl, so an invalid vector length reaches sve_state_size_from_vl() and the WARN_ON() there, which is fatal at EL2. The existing !sve_state_size test rejects such a length, but only after the macro has run.  Check sve_vl_valid() before deriving the state size. A valid length cannot yield a zero size, so the !sve_state_size test goes with it.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | bpftool6.18 amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | bpftool6.18-debuginfo amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | kernel-livepatch-6.18.56-125.164 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | kernel6.18 amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | kernel6.18-debuginfo amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | kernel6.18-debuginfo-common-aarch64 amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | kernel6.18-debuginfo-common-x86_64 amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | kernel6.18-devel amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | kernel6.18-headers amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | kernel6.18-modules-extra amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | kernel6.18-modules-extra-common amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | kernel6.18-tools amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | kernel6.18-tools-debuginfo amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | kernel6.18-tools-devel amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | linux Debian 14 | 7.2.9-1 | [DEBIAN-CVE-2026-98638](https://patchblox.com/security/data/fix/linux/debian-cve-2026-98638.md) | Oct 19, 2026 |
| Linux | microvm-kernel6.18 amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | perf6.18 amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | perf6.18-debuginfo amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | python3-perf6.18 amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |
| Linux | python3-perf6.18-debuginfo amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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