CWE-243 Variant Draft High likelihood

Creation of chroot Jail Without Changing Working Directory

This vulnerability occurs when a program creates a chroot jail but fails to change its current working directory afterward. Because the process's working directory remains outside the jail,…

Definition

What is CWE-243?

This vulnerability occurs when a program creates a chroot jail but fails to change its current working directory afterward. Because the process's working directory remains outside the jail, attackers can use relative paths to access files and directories that should be restricted.
The chroot() system call isolates a process within a specific directory subtree, known as a jail. However, a critical step is often missed: chroot() does not automatically change the process's current working directory. If the working directory remains outside the new root, any relative path operations (like opening '../etc/passwd') can still traverse the original filesystem, completely bypassing the intended isolation. To properly secure the jail, you must immediately call chdir('/') after chroot(). This changes the working directory to be inside the new root, ensuring all subsequent relative path references are confined. Without this step, the chroot jail provides a false sense of security and is trivial for an attacker to escape.
Auswirkungen in der Praxis

Real-world CVEs caused by CWE-243

Bisher sind in MITREs Katalog keine öffentlichen CVE-Referenzen mit dieser CWE verknüpft.

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

Consider the following source code from a (hypothetical) FTP server:

Verwundbar C 
chroot("/var/ftproot");
  ...
  fgets(filename, sizeof(filename), network);
  localfile = fopen(filename, "r");
  while ((len = fread(buf, 1, sizeof(buf), localfile)) != EOF) {
  	fwrite(buf, 1, sizeof(buf), network);
  }
  fclose(localfile);
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-243

  • 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-243

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-243 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-243?

This vulnerability occurs when a program creates a chroot jail but fails to change its current working directory afterward. Because the process's working directory remains outside the jail, attackers can use relative paths to access files and directories that should be restricted.

Wie gravierend ist CWE-243?

MITRE stuft die Exploit-Wahrscheinlichkeit als hoch ein — diese Schwachstelle wird aktiv in freier Wildbahn ausgenutzt und sollte priorisiert behoben werden.

Welche Sprachen oder Plattformen sind von CWE-243 betroffen?

MITRE lists the following affected platforms: C, C++, Unix.

Wie kann ich CWE-243 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-243?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-243 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-243?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/243.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-243

CWE-669 Parent

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CWE-212 Sibling

Improper Removal of Sensitive Information Before Storage or Transfer

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CWE-434 Sibling

Unrestricted Upload of File with Dangerous Type

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CWE-494 Sibling

Download of Code Without Integrity Check

This vulnerability occurs when an application fetches and runs code from an external source—like a remote server or CDN—without properly…

CWE-565 Sibling

Reliance on Cookies without Validation and Integrity Checking

This vulnerability occurs when an application uses cookies to make security decisions—like granting access or changing settings—but fails…

CWE-829 Sibling

Inclusion of Functionality from Untrusted Control Sphere

This weakness occurs when an application integrates executable code, like a library or plugin, from a source it does not fully control or…

Ressourcen

Further reading

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