The Samba-Bugzilla – Bug 8776
Not all reserved device names are escaped (e.g. LPT4)
Last modified: 2012-02-24 04:33:02 UTC
Samba escapes filenames which cannot be used under Windows, such as COM1, allowing files with these names to be accessed from a Windows machine. However according to the list from Microsoft, there are some reserved names which Samba does not escape and thus those files cannot be accessed from Windows via Samba.
Samba escapes COM[1-3], but not COM[4-9]. It escapes LPT[1-3] but not LPT[4-9].