CVE-2013-5133

Vulnerability

A backup restore operation in Apple iOS prior to version 7.1 does not restrict symbolic links (symlinks) contained within backup data. When a user restores a maliciously crafted backup, the symlink is restored to the filesystem, and subsequent write operations during the restore process can follow the symlink and write to unintended locations outside the backup scope. This issue affects iPhone 4 and later, iPod touch (5th generation) and later, and iPad 2 and later running iOS versions before 7.1 [1].

Exploitation

An attacker must provide a crafted backup containing a symbolic link pointing to an arbitrary filesystem path. During a restore operation performed by the victim, the restore process recreates the symlink, and any subsequent file writes that occur as part of the restore procedure follow the symlink, enabling the attacker to write data to arbitrary locations on the device. No special network position or authentication is required beyond the ability to deliver the malicious backup to the user, who must then restore it [1].

Impact

Successful exploitation allows an attacker to overwrite arbitrary files on the device during the restore process. This can lead to unauthorized modification of system files, configuration data, or user content, potentially resulting in persistent compromise or privilege escalation. The confidentiality and availability of the device may also be affected, depending on the files targeted [1].

Mitigation

Apple addressed this issue in iOS 7.1, which checks for symbolic links during the restore process and prevents them from being followed to arbitrary locations. Users should update their devices to iOS 7.1 or later to protect against this vulnerability. No workaround is available for unpatched versions [1].