CWE-271 Class Incomplete High likelihood

Privilege Dropping / Lowering Errors

This vulnerability occurs when a system or process fails to reduce its elevated permissions before transferring control of a resource to a less-privileged user or component.

Definition

What is CWE-271?

This vulnerability occurs when a system or process fails to reduce its elevated permissions before transferring control of a resource to a less-privileged user or component.
In secure software design, a common practice is for a high-privilege process to perform a sensitive operation and then immediately lower its permissions before interacting with lower-privileged entities. This flaw breaks that chain of trust. When a system hands off a file, process, or network connection without first dropping these elevated rights, it effectively grants those high-level permissions to the receiving party, which may not be authorized to have them. This creates a dangerous privilege escalation path. By failing to contain permissions within their intended scope, the flaw allows excessive access to spread throughout the application environment. An attacker who gains control of the lower-privileged component can then inherit and abuse these unintended permissions, potentially taking full control of the system or accessing restricted data.
Auswirkungen in der Praxis

Real-world CVEs caused by CWE-271

  • CVE-2000-1213

    Program does not drop privileges after acquiring the raw socket.

  • CVE-2001-0559

    Setuid program does not drop privileges after a parsing error occurs, then calls another program to handle the error.

  • CVE-2001-0787

    Does not drop privileges in related groups when lowering privileges.

  • CVE-2002-0080

    Does not drop privileges in related groups when lowering privileges.

  • CVE-2001-1029

    Does not drop privileges before determining access to certain files.

  • CVE-1999-0813

    Finger daemon does not drop privileges when executing programs on behalf of the user being fingered.

  • CVE-1999-1326

    FTP server does not drop privileges if a connection is aborted during file transfer.

  • CVE-2000-0172

    Program only uses seteuid to drop privileges.

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 calls chroot() to restrict the application to a subset of the filesystem below APP_HOME in order to prevent an attacker from using the program to gain unauthorized access to files located elsewhere. The code then opens a file specified by the user and processes the contents of the file.

Verwundbar C 
chroot(APP_HOME);
  chdir("/");
  FILE* data = fopen(argv[1], "r+");
  ...
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-271

  • Architecture and Design Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
  • Architecture and Design / Operation Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.
  • Architecture and Design Consider following the principle of separation of privilege. Require multiple conditions to be met before permitting access to a system resource.
Erkennungssignale

How to detect CWE-271

SAST High

Führe statische Analyse (SAST) auf der Codebasis aus und suche im Datenfluss nach dem unsicheren Muster.

DAST Moderate

Führe dynamische Application-Security-Tests gegen den Live-Endpoint aus.

Runtime Moderate

Beobachte Runtime-Logs auf ungewöhnliche Exception-Traces, fehlerhafte Eingaben oder Versuche, Autorisierung zu umgehen.

Code review Moderate

Code Review: Markiere jeden neuen Code, der Eingaben von dieser Oberfläche ohne validierte Framework-Helper verarbeitet.

Plexicus Auto-Fix

Plexicus erkennt CWE-271 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-271?

This vulnerability occurs when a system or process fails to reduce its elevated permissions before transferring control of a resource to a less-privileged user or component.

Wie gravierend ist CWE-271?

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-271 betroffen?

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

Wie kann ich CWE-271 verhindern?

Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to…

Wie erkennt und behebt Plexicus CWE-271?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-271 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-271?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/271.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-271

CWE-269 Parent

Improper Privilege Management

This vulnerability occurs when an application fails to correctly manage user permissions, allowing someone to perform actions or access…

CWE-250 Sibling

Execution with Unnecessary Privileges

This vulnerability occurs when software runs with higher permissions than it actually needs to perform its tasks. This excessive privilege…

CWE-266 Sibling

Incorrect Privilege Assignment

This vulnerability occurs when a system mistakenly grants a user, process, or entity a specific permission or privilege they should not…

CWE-267 Sibling

Privilege Defined With Unsafe Actions

This vulnerability occurs when a system grants a user, role, or process a specific permission that can be misused to perform dangerous,…

CWE-268 Sibling

Privilege Chaining

Privilege chaining occurs when an attacker combines two separate permissions or capabilities, neither of which is dangerous on its own, to…

CWE-270 Sibling

Privilege Context Switching Error

This vulnerability occurs when an application fails to properly manage user permissions while moving between different security contexts,…

CWE-274 Sibling

Improper Handling of Insufficient Privileges

This vulnerability occurs when an application fails to properly manage situations where it lacks the necessary permissions to execute an…

CWE-648 Sibling

Incorrect Use of Privileged APIs

This vulnerability occurs when software incorrectly uses functions that require special permissions. Attackers can exploit these mistakes…

CWE-272 Child

Least Privilege Violation

This vulnerability occurs when software fails to reduce its elevated system privileges after completing a sensitive operation, leaving it…

Ressourcen

Further reading

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