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CVE-2026-64298 is an authorization flaw in the Linux kernel NFSv4 client handling of open() requests with O_TRUNC. The nfs_open_permission_mask() function derived the authorization mask solely from O_ACCMODE and did not add MAY_WRITE when O_TRUNC was present. Consequently, an open(O_RDONLY | O_TRUNC) request by a caller lacking write permission could pass the local MAY_READ check when the client satisfied the operation from a cached write delegation through the delegated-open path. The client subsequently issued SETATTR(size=0) using the write-delegation stateid, allowing the NFS server to accept truncation despite the caller's lack of write authorization. The fix adds MAY_WRITE to the permission mask whenever O_TRUNC is specified, causing unauthorized requests to fail with EACCES as required by POSIX.
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Linux kernel NFSv4 permission-validation flaw in which the open permission mask omits MAY_WRITE for O_TRUNC.
A Linux kernel vulnerability addressed by the Oracle Linux patch; no flaw details are provided.
A vulnerability addressed by AlmaLinux ALSA-2026:63014 affecting listed AlmaLinux 8 kernel packages.
A vulnerability referenced by the AlmaLinux ALSA-2026:63013 security advisory for AlmaLinux 8 kernel-rt packages.
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Every observed campaign linking this CVE to a named adversary.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.