CVE-2026-64298

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> NFSv4: include MAY_WRITE in open permission mask for O_TRUNC<br /> <br /> POSIX requires write permission to truncate a file, so an open() that<br /> specifies O_TRUNC must be authorized for write access regardless of the<br /> O_ACCMODE access mode.<br /> <br /> nfs_open_permission_mask() builds the access mask passed to<br /> nfs_may_open(), which is the local authorization gate for OPENs the<br /> client serves itself from a cached write delegation via the<br /> can_open_delegated() path in nfs4_try_open_cached(). The mask is<br /> derived from O_ACCMODE alone, so an open(O_RDONLY | O_TRUNC) against a<br /> file the caller cannot write requests only MAY_READ and passes the<br /> local check. The OPEN is then satisfied locally and the truncation is<br /> issued to the server as a SETATTR(size=0) over the delegation stateid,<br /> which the server accepts under standard write-delegation semantics.<br /> POSIX requires that this open fail with EACCES.<br /> <br /> Include MAY_WRITE in the mask whenever O_TRUNC is set so the local<br /> check matches the access the server would have enforced.