CWE-58: Path Equivalence: Windows 8.3 Filename

Definition

What is CWE-58?

This vulnerability occurs when an application's security controls successfully block access to a file's full name on Windows, but fail to protect the shorter 8.3 format version of the same filename, creating a bypassable loophole.

Windows maintains backward compatibility by automatically generating a short 8.3 filename (like 'DOCUME~1.TXT') for files with longer names. This creates two distinct paths to the same file. If your access control checks only validate the long filename, attackers can simply use the equivalent short name to bypass your restrictions. This is a classic path equivalence flaw where the system sees 'LONGFILENAME.DOC' and 'LONGFI~1.DOC' as different strings, even though they point to the same underlying resource. Developers must normalize and validate both naming formats in their security logic to close this gap.

Real-world impact

Real-world CVEs caused by CWE-58

CVE-1999-0012

Multiple web servers allow restriction bypass using 8.3 names instead of long names
CVE-2001-0795

Source code disclosure using 8.3 file name.
CVE-2005-0471

Multi-Factor Vulnerability. Product generates temporary filenames using long filenames, which become predictable in 8.3 format.

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.

Vulnerable pseudo

// 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-58

System Configuration Disable Windows from supporting 8.3 filenames by editing the Windows registry. Preventing 8.3 filenames will not remove previously generated 8.3 filenames.

Detection signals

How to detect CWE-58

SAST High

Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.

DAST Moderate

Run dynamic application security testing against the live endpoint.

Runtime Moderate

Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.

Code review Moderate

Code review: flag any new code that handles input from this surface without using the validated framework helpers.

CWE-58

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Frequently asked questions

What is CWE-58?

This vulnerability occurs when an application's security controls successfully block access to a file's full name on Windows, but fail to protect the shorter 8.3 format version of the same filename, creating a bypassable loophole.

How serious is CWE-58?

MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.

What languages or platforms are affected by CWE-58?

MITRE lists the following affected platforms: Windows.

How can I prevent CWE-58?

Disable Windows from supporting 8.3 filenames by editing the Windows registry. Preventing 8.3 filenames will not remove previously generated 8.3 filenames.

How does Plexicus detect and fix CWE-58?

Plexicus's SAST engine matches the data-flow signature for CWE-58 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-58?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/58.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-58

CWE-41 Parent

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Path Equivalence: Windows 8.3 Filename

What is CWE-58?

Real-world CVEs caused by CWE-58

Step-by-step attacker path

Vulnerable pseudo

Secure pseudo

How to prevent CWE-58

How to detect CWE-58

Don't catalog this weakness. Prove it's reachable.

Frequently asked questions

Weaknesses related to CWE-58

Improper Resolution of Path Equivalence

Path Equivalence: 'filename.' (Trailing Dot)

Path Equivalence: 'file.name' (Internal Dot)

Path Equivalence: 'filename ' (Trailing Space)

Path Equivalence: ' filename' (Leading Space)

Path Equivalence: 'file name' (Internal Whitespace)

Path Equivalence: 'filename/' (Trailing Slash)

Path Equivalence: '//multiple/leading/slash'

Path Equivalence: '/multiple//internal/slash'

Further reading

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Sample evidence handover

Server-Side Request Forgery in `webhooks/receiver`