Concon
Encyclopedia
Con/con is a computer bug that appeared in the Windows 95
and Windows 98
operating system
s. The name comes from the fact that referring to the file "C:\con\con" would crash
these systems. This was a particular case of a more general bug, where the system failed to respond correctly to file path
s containing multiple device file names. (In the example, "con" is the device file name for the console device.) Such file paths are invalid on Windows, because device file names are reserved word
s. Even though the system would report an error if "C:\con" were accessed, the system would miss the attempted reference to "con" in the case of accessing "C:\con\con".
This bug was considered a security vulnerability because malicious web pages could crash systems with links such as file:///C:/con/con. A patch released by Microsoft in March 16, 2000 fixes the bug and the vulnerability.
Windows 95
Windows 95 is a consumer-oriented graphical user interface-based operating system. It was released on August 24, 1995 by Microsoft, and was a significant progression from the company's previous Windows products...
and Windows 98
Windows 98
Windows 98 is a graphical operating system by Microsoft. It is the second major release in the Windows 9x line of operating systems. It was released to manufacturing on 15 May 1998 and to retail on 25 June 1998. Windows 98 is the successor to Windows 95. Like its predecessor, it is a hybrid...
operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
s. The name comes from the fact that referring to the file "C:\con\con" would crash
Crash (computing)
A crash in computing is a condition where a computer or a program, either an application or part of the operating system, ceases to function properly, often exiting after encountering errors. Often the offending program may appear to freeze or hang until a crash reporting service documents...
these systems. This was a particular case of a more general bug, where the system failed to respond correctly to file path
Path (computing)
A path, the general form of a filename or of a directory name, specifies a unique location in a file system. A path points to a file system location by following the directory tree hierarchy expressed in a string of characters in which path components, separated by a delimiting character, represent...
s containing multiple device file names. (In the example, "con" is the device file name for the console device.) Such file paths are invalid on Windows, because device file names are reserved word
Reserved word
Reserved words are one type of grammatical construct in programming languages. These words have special meaning within the language and are predefined in the language’s formal specifications...
s. Even though the system would report an error if "C:\con" were accessed, the system would miss the attempted reference to "con" in the case of accessing "C:\con\con".
This bug was considered a security vulnerability because malicious web pages could crash systems with links such as file:///C:/con/con. A patch released by Microsoft in March 16, 2000 fixes the bug and the vulnerability.