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.)
CWE-243 Variante Brouillon
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,…
Définition
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.
Impact réel
Real-world CVEs caused by CWE-243
Aucune référence CVE publique n'est liée à ce CWE dans le catalogue MITRE pour le moment.
Comment les attaquants l'exploitent
Parcours de l'attaquant étape par étape
- 1
Identifier un chemin de code qui traite des entrées non fiables sans validation.
- 2
Élaborer une charge utile qui exploite le comportement non sécurisé — injection, traversal, débordement ou abus de logique.
- 3
Délivrer la charge utile via une requête normale et observer la réaction de l'application.
- 4
Itérer jusqu'à ce que la réponse divulgue des données, exécute le code de l'attaquant ou élève les privilèges.
Exemple de code vulnérable
Vulnerable C
Consider the following source code from a (hypothetical) FTP server:
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); Exemple de code sécurisé
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.
Liste de contrôle de prévention
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.
Signaux de détection
How to detect CWE-243
CWE-243
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Questions fréquentes Qu'est-ce que CWE-243 ?
Quelle est la gravité de CWE-243 ?
Quels langages ou plateformes sont affectés par CWE-243 ?
Comment puis-je prévenir CWE-243 ?
Comment Plexicus détecte et corrige CWE-243 ?
Où puis-je en savoir plus sur CWE-243 ?
Frequently asked questions
Qu'est-ce que 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.
Quelle est la gravité de CWE-243 ?
MITRE évalue la probabilité d'exploitation comme Élevée — cette faiblesse est activement exploitée et doit être priorisée pour la remédiation.
Quels langages ou plateformes sont affectés par CWE-243 ?
MITRE lists the following affected platforms: C, C++, Unix.
Comment puis-je prévenir CWE-243 ?
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.
Comment Plexicus détecte et corrige CWE-243 ?
Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-243 à chaque commit. Lorsqu'une correspondance est trouvée, notre agent Codex Remedium ouvre une PR de correction avec le code corrigé, les tests et un résumé d'une ligne pour le relecteur.
Où puis-je en savoir plus sur CWE-243 ?
MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/243.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.
Faiblesses associées
Weaknesses related to CWE-243
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Unrestricted Upload of File with Dangerous Type
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Download of Code Without Integrity Check
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CWE-565 Frère
Reliance on Cookies without Validation and Integrity Checking
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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…
Ressources
Further reading
- MITRE — CWE-243 officiel https://cwe.mitre.org/data/definitions/243.html
- Seven Pernicious Kingdoms: A Taxonomy of Software Security Errors https://samate.nist.gov/SSATTM_Content/papers/Seven%20Pernicious%20Kingdoms%20-%20Taxonomy%20of%20Sw%20Security%20Errors%20-%20Tsipenyuk%20-%20Chess%20-%20McGraw.pdf
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