Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.
CWE-64 Variant Incomplete
Windows Shortcut Following (.LNK)
This vulnerability occurs when an application opens a file or directory without properly validating that it is a Windows shortcut (.LNK). If the shortcut's target points to a location outside the…
Definition
What is CWE-64?
This vulnerability occurs when an application opens a file or directory without properly validating that it is a Windows shortcut (.LNK). If the shortcut's target points to a location outside the application's intended security boundary, an attacker can trick the software into accessing unauthorized files.
Windows shortcut files (.LNK) contain a reference to a target file or folder, but they are separate objects with their own permissions. An application that fails to resolve the shortcut's final destination before performing operations can be manipulated. An attacker can place a malicious .LNK file in a location the application trusts, but configure it to point to a sensitive system file or a directory they shouldn't have access to, effectively bypassing intended access controls.
This allows for unauthorized file reads or writes. For example, an application designed to process user-uploaded files in a sandboxed folder could be tricked into reading the Windows SAM database or overwriting a critical configuration file because it blindly follows the shortcut. The core security failure is not canonicalizing the path to the shortcut's true target and checking if that resolved path is within the allowed scope before proceeding.
Real-world impact
Real-world CVEs caused by CWE-64
-
network access control service executes program with high privileges and allows symlink to invoke another executable or perform DLL injection.
-
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."
-
FTP server allows remote attackers to read arbitrary files and directories by uploading a .lnk (link) file that points to the target file.
-
FTP server allows remote attackers to read arbitrary files and directories by uploading a .lnk (link) file that points to the target file.
-
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.
-
".LNK." - .LNK with trailing dot
-
Rootkits can bypass file access restrictions to Windows kernel directories using NtCreateSymbolicLinkObject function to create symbolic link
How attackers exploit it
Step-by-step attacker path
- 1
Identify a code path that handles untrusted input without validation.
- 2
Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.
- 3
Deliver the payload through a normal request and observe the application's reaction.
- 4
Iterate until the response leaks data, executes attacker code, or escalates privileges.
Vulnerable code example
Vulnerable pseudo
MITRE has not published a code example for this CWE. The pattern below is illustrative — see Resources for canonical references.
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
// Untrusted input flows directly into the sensitive sink.
return executeUnsafe(input);
} Secure code example
Secure pseudo
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
const safe = validateAndEscape(input);
return executeWithGuards(safe);
} What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist
How to prevent CWE-64
- Architecture and Design 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.
Detection signals
How to detect CWE-64
Run dynamic application security testing against the live endpoint.
Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.
Code review: flag any new code that handles input from this surface without using the validated framework helpers.
CWE-64
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Frequently asked questions What is CWE-64?
How serious is CWE-64?
What languages or platforms are affected by CWE-64?
How can I prevent CWE-64?
How does Plexicus detect and fix CWE-64?
Where can I learn more about CWE-64?
Frequently asked questions
What is CWE-64?
This vulnerability occurs when an application opens a file or directory without properly validating that it is a Windows shortcut (.LNK). If the shortcut's target points to a location outside the application's intended security boundary, an attacker can trick the software into accessing unauthorized files.
How serious is CWE-64?
MITRE rates the likelihood of exploit as Low — exploitation is uncommon, but the weakness should still be fixed when discovered.
What languages or platforms are affected by CWE-64?
MITRE lists the following affected platforms: Windows.
How can I prevent CWE-64?
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.
How does Plexicus detect and fix CWE-64?
Plexicus's SAST engine matches the data-flow signature for CWE-64 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.
Where can I learn more about CWE-64?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/64.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-64
CWE-59 Parent
Improper Link Resolution Before File Access ('Link Following')
This vulnerability occurs when an application uses a filename to access a file but fails to properly check if that name points to a…
CWE-1386 Sibling
Insecure Operation on Windows Junction / Mount Point
This vulnerability occurs when a Windows application opens a file or directory without properly validating that the path is not a symbolic…
CWE-61 Sibling
UNIX Symbolic Link (Symlink) Following
This vulnerability occurs when a software application opens files or directories without properly checking if they are symbolic links…
CWE-62 Sibling
UNIX Hard Link
This vulnerability occurs when an application opens a file or directory without verifying if the name points to a hard link that leads…
CWE-65 Sibling
Windows Hard Link
This vulnerability occurs when a Windows application opens a file or directory without properly verifying if the path points to a hard…
Ready to validate what matters?
Ready to validate what matters?
Plexicus is Proof-Driven AppSec: validated findings, contextual understanding, and reviewed remediation — anchored in evidence, scoped with you.