Inconsistent handling of O_CREATE|O_EXCL on Unix and Windows in os in syscall

Vulnerability Description

os.OpenFile(path, os.O_CREATE|O_EXCL) behaved differently on Unix and Windows systems when the target path was a dangling symlink. On Unix systems, OpenFile with O_CREATE and O_EXCL flags never follows symlinks. On Windows, when the target path was a symlink to a nonexistent location, OpenFile would create a file in that location. OpenFile now always returns an error when the O_CREATE and O_EXCL flags are both set and the target path is a symlink.

References

• https://go.dev/cl/672396
• https://go.dev/issue/73702
• https://groups.google.com/g/golang-announce/c/ufZ8WpEsA3A
• https://pkg.go.dev/vuln/GO-2025-3750