How severe is CVE-2026-64561?

No CVSS score has been assigned to CVE-2026-64561 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-64561?

CVE-2026-64561 affects the following packages: Kernel (Linux). Ecosystems affected: Linux.

How do I fix CVE-2026-64561?

Update Kernel to 6.6.148 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-64561 is resolved across your whole dependency graph.

How do I detect CVE-2026-64561 in my Linux dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Kernel. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2026-64561 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-64561?

O3 pinpoints whether CVE-2026-64561 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2026-64561 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-64561 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was CVE-2026-64561 published, and has it been updated?

CVE-2026-64561 was published on August 4, 2026 and was last updated on August 5, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐧 Linux

CVE-2026-64561

CVE-2026-64561 is a security vulnerability in Kernel. O3 Security confirms whether CVE-2026-64561 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

KVM: x86: Check for invalid/obsolete root *after* making MMU pages available

Published

Aug 4, 2026

Updated

Aug 5, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Real-World Exposure

1 pkg affected

🐧Kernel

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Linux packages — download data is not available via public APIs for these ecosystems.

Description

In the Linux kernel, the following vulnerability has been resolved:

KVM: x86: Check for invalid/obsolete root after making MMU pages available

Check for a "stale" page fault, i.e. for an invalid and/or obsolete root, after making MMU pages available for the shadow MMU. If reclaiming shadow pages zaps an in-use root, i.e. marks it invalid, then KVM will attempt to map memory into an invalid root. On its own, populating an invalid root is "fine", but because child shadow pages inherit their parent's role, any children created during the map/fetch will be created as invalid pages, thus violating KVM's invariant that invalid pages are never on the list of active MMU pages.

Note, the underlying flaw has existed since KVM first started tracking invalid roots in 2008 (commit 2e53d63acba7, "KVM: MMU: ignore zapped root pagetables"), but the true badness only came along in 2020 (Linux 5.9) with the invariant that invalid shadow pages can't be on the list of active pages.

Note #2, inheriting role.invalid when creating child shadow pages is also far from ideal; that flaw will be addressed separately.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐧Linux	`Kernel`	≥ 5.9.0&&< 6.6.148	6.6.148

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Kernel. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update Kernel to 6.6.148 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-64561 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-64561 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2026-64561. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Check for invalid/obsolete root *after* making MMU pages available Check for a "stale" page fault, i.e. for an invalid and/or obsolete root, after making MMU pages available for the shadow MMU. If reclaiming shadow pages zaps an in-use root, i.e. marks it invalid, then KVM will attempt to map memory into an invalid root. On its own, populating an invalid root is "fine", but because child shadow pages inherit their parent's role, any children created during the map/fetch will be created as invalid pages, thus viol

O3 Security · Impact-Aware SCA

Is CVE-2026-64561 in your dependencies?

O3 detects CVE-2026-64561 across Linux dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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