CWE-379 Base Incomplete Low likelihood

Creation of Temporary File in Directory with Insecure Permissions

This vulnerability occurs when an application creates a temporary file in a directory that is too permissive, allowing unauthorized users or processes to see, access, or manipulate the file.

Definition

What is CWE-379?

This vulnerability occurs when an application creates a temporary file in a directory that is too permissive, allowing unauthorized users or processes to see, access, or manipulate the file.
When a temporary file is placed in a directory with loose permissions (like world-readable or world-writable), other users or system actors can detect its presence. This simple act of discovery reveals which application created the file, offering a window into what the user is currently doing. Attackers can correlate this information with running processes to infer sensitive user activity, turning a seemingly minor information leak into a serious privacy breach. This issue is more than just a file access problem; it's an information exposure flaw that can enable targeted attacks. By knowing which application is in use, an attacker gains critical context to craft further exploits, potentially escalating privileges or accessing confidential data. Developers must ensure temporary files are created in secure, private locations with strict access controls to prevent this form of reconnaissance.
Auswirkungen in der Praxis

Real-world CVEs caused by CWE-379

  • CVE-2022-27818

    A hotkey daemon written in Rust creates a domain socket file underneath /tmp, which is accessible by any user.

  • CVE-2021-21290

    A Java-based application for a rapid-development framework uses File.createTempFile() to create a random temporary file with insecure default permissions.

Wie Angreifer es ausnutzen

Angreiferpfad Schritt für Schritt

  1. 1

    In the following code examples a temporary file is created and written to. After using the temporary file, the file is closed and deleted from the file system.

  2. 2

    However, within this C/C++ code the method tmpfile() is used to create and open the temp file. The tmpfile() method works the same way as the fopen() method would with read/write permission, allowing attackers to read potentially sensitive information contained in the temp file or modify the contents of the file.

  3. 3

    Similarly, the createTempFile() method used in the Java code creates a temp file that may be readable and writable to all users.

  4. 4

    Additionally both methods used above place the file into a default directory. On UNIX systems the default directory is usually "/tmp" or "/var/tmp" and on Windows systems the default directory is usually "C:\\Windows\\Temp", which may be easily accessible to attackers, possibly enabling them to read and modify the contents of the temp file.

Verwundbares Codebeispiel

Vulnerable C

In the following code examples a temporary file is created and written to. After using the temporary file, the file is closed and deleted from the file system.

Verwundbar C 
FILE *stream;
  if( (stream = tmpfile()) == NULL ) {
  		perror("Could not open new temporary file\n");
  		return (-1);
  }
```
// write data to tmp file* 
  ...
  // remove tmp file
  rmtmp();
Sicheres Codebeispiel

Secure pseudo

Sicher 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.
Präventions-Checkliste

How to prevent CWE-379

  • Requirements Many contemporary languages have functions which properly handle this condition. Older C temp file functions are especially susceptible.
  • Implementation Try to store sensitive tempfiles in a directory which is not world readable -- i.e., per-user directories.
  • Implementation Avoid using vulnerable temp file functions.
Erkennungssignale

How to detect CWE-379

Automated Static Analysis High

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Plexicus Auto-Fix

Plexicus erkennt CWE-379 automatisch und öffnet in unter 60 Sekunden einen Fix-PR.

Codex Remedium scannt jeden Commit, identifiziert genau diese Schwachstelle und liefert einen reviewer-ready Pull Request mit dem Patch. Keine Tickets. Keine Hand-offs.

Demo anfordern Plexicus kostenlos testen
Häufig gestellte Fragen

Frequently asked questions

Was ist CWE-379?

This vulnerability occurs when an application creates a temporary file in a directory that is too permissive, allowing unauthorized users or processes to see, access, or manipulate the file.

Wie gravierend ist CWE-379?

MITRE stuft die Exploit-Wahrscheinlichkeit als niedrig ein — eine Ausnutzung ist selten, die Schwachstelle sollte aber dennoch behoben werden, sobald sie entdeckt wird.

Welche Sprachen oder Plattformen sind von CWE-379 betroffen?

MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.

Wie kann ich CWE-379 verhindern?

Many contemporary languages have functions which properly handle this condition. Older C temp file functions are especially susceptible. Try to store sensitive tempfiles in a directory which is not world readable -- i.e., per-user directories.

Wie erkennt und behebt Plexicus CWE-379?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-379 bei jedem Commit. Bei einem Treffer öffnet unser Codex-Remedium-Agent einen Fix-PR mit korrigiertem Code, Tests und einer einzeiligen Zusammenfassung für den Reviewer.

Wo erfahre ich mehr über CWE-379?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/379.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-379

CWE-377 Parent

Insecure Temporary File

This vulnerability occurs when an application creates temporary files with insecure permissions or in predictable locations, allowing…

CWE-378 Sibling

Creation of Temporary File With Insecure Permissions

This vulnerability occurs when a program creates a temporary file but sets its file permissions too loosely, allowing other users or…

Ressourcen

Further reading

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