CVE-2026-89687

In the Linux kernel, the following vulnerability has been resolved:

nfsd: ensure nfsd file do acquire() does not use a non-opened file

->atomic open is permitted to return success without actually opening the file. It indicates this by calling finish no open(). This means dentry create() can return a file which hasn't been opened. This is extremely unlikely as ->atomic open handlers typically use finish no open() only for already existing files, and dentry create() isn't called in that case, and the parent being locked should prevent races.

However out of an abundance of caution it seems wise to teach nfsd to only use the file returned by dentry create() if FMODE OPENED is set, indicating that it has in fact been opened.