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CVE-2025-39840 is an out-of-bounds read in the Linux kernel audit subsystem's audit_compare_dname_path() function. When an audit watch targets the root directory and an fsnotify event concerns a single-character name immediately beneath root, parent_len() returns 1 and the path-handling logic reduces pathlen to zero. The subsequent loop can dereference p[pathlen - 1], resulting in an access at p[-1]. The fix adds a pathlen > 0 guard to the loop condition before the indexed dereference.
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A Linux kernel audit subsystem out-of-bounds read in audit_compare_dname_path(). It is triggered when an audit watch on the root directory is combined with an fsnotify event for a single-character file directly beneath root. The vulnerable logic can dereference p[-1] when the computed path length is zero.
A Linux kernel vulnerability in the audit subsystem involving an out-of-bounds read in audit_compare_dname_path().
A Linux kernel vulnerability in the audit subsystem involving an out-of-bounds read in audit_compare_dname_path().
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