CWE-72 Variant Incomplete

Improper Handling of Apple HFS+ Alternate Data Stream Path

This vulnerability occurs when software fails to correctly process HFS+ file system paths that point to alternate data streams, such as a file's data or resource fork.

Definition

What is CWE-72?

This vulnerability occurs when software fails to correctly process HFS+ file system paths that point to alternate data streams, such as a file's data or resource fork.
When an application makes security or logic decisions based solely on a file's main path, an attacker can bypass these controls by specifying an alternate stream path instead. For example, a validation check that allows '/safe/file.txt' might also unintentionally allow '/safe/file.txt/..namedfork/data', granting access to the same file through a different channel. This can lead to two primary risks. First, access restrictions can be circumvented if the software doesn't recognize that the alternate stream path refers to the same underlying file. Second, if the application performs different actions based on file extensions or names, feeding it a resource fork path could trigger unexpected and potentially dangerous behavior, as the code is now interacting with a different part of the file than intended.
Real-world impact

Real-world CVEs caused by CWE-72

  • CVE-2004-1084

    Server allows remote attackers to read files and resource fork content via HTTP requests to certain special file names related to multiple data streams in HFS+.

How attackers exploit it

Step-by-step attacker path

  1. 1

    Identify a code path that handles untrusted input without validation.

  2. 2

    Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.

  3. 3

    Deliver the payload through a normal request and observe the application's reaction.

  4. 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

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-72

  • Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
  • Implementation Validate input at trust boundaries; use allowlists, not denylists.
  • Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
  • Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
  • Operation Monitor logs for the runtime signals listed in the next section.
Detection signals

How to detect CWE-72

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.

Plexicus auto-fix

Plexicus auto-detects CWE-72 and opens a fix PR in under 60 seconds.

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Frequently asked questions

Frequently asked questions

What is CWE-72?

This vulnerability occurs when software fails to correctly process HFS+ file system paths that point to alternate data streams, such as a file's data or resource fork.

How serious is CWE-72?

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-72?

MITRE lists the following affected platforms: macOS.

How can I prevent CWE-72?

Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.

How does Plexicus detect and fix CWE-72?

Plexicus's SAST engine matches the data-flow signature for CWE-72 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-72?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/72.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-72

CWE-66 Parent

Improper Handling of File Names that Identify Virtual Resources

This vulnerability occurs when software incorrectly processes a filename that points to a 'virtual' resource—like a device, pipe, or…

CWE-67 Sibling

Improper Handling of Windows Device Names

This vulnerability occurs when an application builds file paths from user input but fails to properly recognize or handle Windows reserved…

CWE-69 Sibling

Improper Handling of Windows ::DATA Alternate Data Stream

This vulnerability occurs when an application fails to properly secure or monitor Windows Alternate Data Streams (ADS), allowing them to…

Resources

Further reading

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