CWE-377 Class Incomplete

Insecure Temporary File

This vulnerability occurs when an application creates temporary files with insecure permissions or in predictable locations, allowing attackers to read, modify, or delete sensitive data.

Definition

What is CWE-377?

This vulnerability occurs when an application creates temporary files with insecure permissions or in predictable locations, allowing attackers to read, modify, or delete sensitive data.
Insecure temporary files are a common but dangerous flaw. They happen when developers use predictable filenames, place files in world-writable directories, or set overly permissive file access rights. Attackers can exploit this by 'symlinking' a predictable filename to a critical system file, performing a race condition to replace the file after creation, or simply reading the exposed data. This can lead to information disclosure, data corruption, or even a full system compromise. Preventing this requires using secure, random filenames, setting restrictive file permissions (like 0600), and leveraging secure system APIs designed for temporary file creation. Managing this at scale across numerous applications is difficult; an ASPM like Plexicus can help you track and remediate these flaws across your entire stack. While SAST tools catch the pattern, Plexicus uses AI to suggest the actual code fix, such as replacing insecure `tmpnam()` calls with secure `mkstemp()`, saving hours of manual work.
Auswirkungen in der Praxis

Real-world CVEs caused by CWE-377

  • CVE-2022-41954

    A library uses the Java File.createTempFile() method which creates a file with "-rw-r--r--" default permissions on Unix-like operating systems

Wie Angreifer es ausnutzen

Angreiferpfad Schritt für Schritt

  1. 1

    Identifiziere einen Codepfad, der nicht vertrauenswürdige Eingaben ohne Validierung verarbeitet.

  2. 2

    Erzeuge eine Payload, die das unsichere Verhalten auslöst — Injection, Traversal, Overflow oder Logik-Missbrauch.

  3. 3

    Liefere die Payload über einen normalen Request aus und beobachte die Reaktion der Anwendung.

  4. 4

    Iteriere, bis die Antwort Daten preisgibt, Angreifer-Code ausführt oder Berechtigungen eskaliert.

Verwundbares Codebeispiel

Vulnerable C

The following code uses a temporary file for storing intermediate data gathered from the network before it is processed.

Verwundbar C 
if (tmpnam_r(filename)) {
  		FILE* tmp = fopen(filename,"wb+");
  		while((recv(sock,recvbuf,DATA_SIZE, 0) > 0)&(amt!=0)) amt = fwrite(recvbuf,1,DATA_SIZE,tmp);
  }
  ...
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-377

  • 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.
Erkennungssignale

How to detect CWE-377

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-377 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-377?

This vulnerability occurs when an application creates temporary files with insecure permissions or in predictable locations, allowing attackers to read, modify, or delete sensitive data.

Wie gravierend ist CWE-377?

MITRE hat für diese Schwachstelle keine Exploit-Wahrscheinlichkeit veröffentlicht. Behandle sie als mittlere Auswirkung, bis dein Threat Model anderes belegt.

Welche Sprachen oder Plattformen sind von CWE-377 betroffen?

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

Wie kann ich CWE-377 verhindern?

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.

Wie erkennt und behebt Plexicus CWE-377?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-377 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-377?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/377.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-377

CWE-668 Parent

Exposure of Resource to Wrong Sphere

This vulnerability occurs when an application unintentionally makes a resource accessible to users or systems that should not have…

CWE-1189 Sibling

Improper Isolation of Shared Resources on System-on-a-Chip (SoC)

This vulnerability occurs when a System-on-a-Chip (SoC) fails to properly separate shared hardware resources between secure (trusted) and…

CWE-1282 Sibling

Assumed-Immutable Data is Stored in Writable Memory

This vulnerability occurs when data that should be permanent and unchangeable—like a bootloader, device IDs, or one-time configuration…

CWE-1327 Sibling

Binding to an Unrestricted IP Address

This vulnerability occurs when software or a service is configured to bind to the IP address 0.0.0.0 (or :: in IPv6), which acts as a…

CWE-1331 Sibling

Improper Isolation of Shared Resources in Network On Chip (NoC)

This vulnerability occurs when a Network on Chip (NoC) fails to properly separate its internal, shared resources—like buffers, switches,…

CWE-134 Sibling

Use of Externally-Controlled Format String

This vulnerability occurs when a program uses a format string from an untrusted, external source (like user input, a network packet, or a…

CWE-200 Sibling

Exposure of Sensitive Information to an Unauthorized Actor

This weakness occurs when an application unintentionally reveals sensitive data to someone who shouldn't have access to it.

CWE-374 Sibling

Passing Mutable Objects to an Untrusted Method

This vulnerability occurs when a function receives a direct reference to mutable data, such as an object or array, instead of a safe copy…

CWE-375 Sibling

Returning a Mutable Object to an Untrusted Caller

This vulnerability occurs when a method directly returns a reference to its internal mutable data, allowing untrusted calling code to…

Ressourcen

Further reading

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