Windows Shortcut Following (.LNK)

Opis

The product, when opening a file or directory, does not sufficiently handle when the file is a Windows shortcut (.LNK) whose target is outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.

Inne nazwy

Windows symbolic link following

symlink

Skutki

• Confidentiality, Integrity

  Read Files or Directories; Modify Files or Directories

  The shortcut (file with the .lnk extension) can permit an attacker to read/write a file that they originally did not have permissions to access.

Zapobieganie

• Architecture and Design · Separation of Privilege

  Follow the principle of least privilege when assigning access rights to entities in a software system.

  Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.

Przykłady podatności

• CVE-2019-19793 network access control service executes program with high privileges and allows symlink to invoke another executable or perform DLL injection.
• CVE-2000-0342 Mail client allows remote attackers to bypass the user warning for executable attachments such as .exe, .com, and .bat by using a .lnk file that refers to the attachment, aka "Stealth Attachment."
• CVE-2001-1042 FTP server allows remote attackers to read arbitrary files and directories by uploading a .lnk (link) file that points to the target file.
• CVE-2001-1043 FTP server allows remote attackers to read arbitrary files and directories by uploading a .lnk (link) file that points to the target file.
• CVE-2005-0587 Browser allows remote malicious web sites to overwrite arbitrary files by tricking the user into downloading a .LNK (link) file twice, which overwrites the file that was referenced in the first .LNK file.
• CVE-2001-1386 ".LNK." - .LNK with trailing dot
• CVE-2003-1233 Rootkits can bypass file access restrictions to Windows kernel directories using NtCreateSymbolicLinkObject function to create symbolic link

Słabość nadrzędna

• CWE-59 Improper Link Resolution Before File Access ('Link Following')

Kiedy powstaje

• Operation

Dotyczy

Not Language-Specific, Windows, Not Technology-Specific

Uwagi

Under-studied. Windows .LNK files are more "portable" than Unix symlinks and have been used in remote exploits. Some Windows API's will access LNK's as if they are regular files, so one would expect that they would be reported more frequently.