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CVE-2026-63940 is a flaw in the Linux kernel's KVM support for AMD SEV in the handling of Port I/O requests associated with string I/O and software scratch area setup. The vulnerable logic did not explicitly ignore Port I/O requests where the request length or count was zero. As a result, code that processed these requests could underflow the effective length when preparing or validating the scratch area, creating incorrect internal state in the KVM SEV handling path. The issue was resolved by explicitly ignoring zero-length or zero-count Port I/O requests before further processing. Available information characterizes this as a defensive correctness fix in KVM SEV request handling rather than a demonstrated crash or fully established exploitation path.
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No public exploit code observed for this vulnerability.
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1 sources tracked across advisories and community write-ups. News coverage will land here when it surfaces.
No news coverage yet. Advisories and community discussion only.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.