title: Insecure parsing of Windows paths with a \??\ prefix in path/filepath
description: The filepath package does not recognize paths with a \??\ prefix as special. On Windows, a path beginning with \??\ is a Root Local Device path equivalent to a path beginning with \\?\. Paths with a \??\ prefix may be used to access arbitrary locations on the system. For example, the path \??\c:\x is equivalent to the more common path c:\x. Before fix, Clean could convert a rooted path such as \a\..\??\b into the root local device path \??\b. Clean will now convert this to .\??\b. Similarly, Join(\, ??, b) could convert a seemingly innocent sequence of path elements into the root local device path \??\b. Join will now convert this to \.\??\b. In addition, with fix, IsAbs now correctly reports paths beginning with \??\ as absolute, and VolumeName correctly reports the \??\ prefix as a volume name. UPDATE: Go 1.20.11 and Go 1.21.4 inadvertently changed the definition of the volume name in Windows paths starting with \?, resulting in filepath.Clean(\?\c:) returning \?\c: rather than \?\c:\ (among other effects). The previous behavior has been restored.
problem types: CWE-41: Improper Resolution of Path Equivalence
affected:
{
vendor: Go standard library
product: path/filepath
collectionURL: https://pkg.go.dev
packageName: path/filepath
versions:
version: 0, lessThan: 1.20.11, status: affected, versionType: semver
version: 1.21.0-0, lessThan: 1.21.4, status: affected, versionType: semver
platforms: windows
programRoutines:
name: Clean
name: volumeNameLen
name: join
name: Abs
name: Base
name: Dir
name: EvalSymlinks
name: Glob
name: IsLocal
name: Join
name: Rel
name: Split
name: VolumeName
name: Walk
name: WalkDir
defaultStatus: unaffected
}
{
vendor: Go standard library
product: internal/safefilepath
collectionURL: https://pkg.go.dev
packageName: internal/safefilepath
versions:
version: 0, lessThan: 1.20.11, status: affected, versionType: semver
version: 1.21.0-0, lessThan: 1.21.4, status: affected, versionType: semver
platforms: windows
programRoutines:
name: fromFS
name: FromFS
defaultStatus: unaffected
}
{
vendor: Go standard library
product: path/filepath
collectionURL: https://pkg.go.dev
packageName: path/filepath
versions:
version: 1.20.11, lessThan: 1.20.12, status: affected, versionType: semver
version: 1.21.4, lessThan: 1.21.5, status: affected, versionType: semver
platforms: windows
programRoutines:
name: volumeNameLen
name: Abs
name: Base
name: Clean
name: Dir
name: EvalSymlinks
name: Glob
name: IsLocal
name: Join
name: Rel
name: Split
name: VolumeName
name: Walk
name: WalkDir
defaultStatus: unaffected
}
