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CVE-2025-39817 is a slab out-of-bounds read in the Linux kernel EFI variable filesystem, efivarfs. In efivarfs_d_compare(), a dentry name shorter than EFI_VARIABLE_GUID_LEN can cause the calculated GUID-related length or offset to become negative. The function then passes the invalid value to memcmp(), resulting in an out-of-bounds read. The condition is reachable during parallel pathname lookups using a malformed filename: one lookup can add an invalid dentry to the dentry hash while a concurrent lookup retrieves it and invokes efivarfs_d_compare(). The flaw was observed in Linux kernel 6.6 and was present in the upstream development branch at the time of reporting.
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A Linux kernel efivarfs slab out-of-bounds vulnerability in efivarfs_d_compare.
A Linux kernel efivarfs vulnerability involving a slab out-of-bounds condition in efivarfs_d_compare.
A Linux kernel efivarfs slab out-of-bounds vulnerability in efivarfs_d_compare.
A Linux kernel efivarfs slab out-of-bounds vulnerability in efivarfs_d_compare.
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Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.