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-273 Base Incomplete
Improper Check for Dropped Privileges
This vulnerability occurs when an application tries to lower its system privileges but fails to verify that the operation was successful.
Definition
What is CWE-273?
This vulnerability occurs when an application tries to lower its system privileges but fails to verify that the operation was successful.
When a program temporarily elevates its permissions to perform a sensitive task, it should reliably revert to a less-privileged state afterward. If the code doesn't properly confirm this privilege drop—perhaps due to a missing error check or a flawed verification logic—the application continues running with its elevated access rights.
This creates a critical security gap, as an attacker could potentially exploit the retained high privileges to perform unauthorized actions, access restricted data, or modify system settings. Essentially, the intended security boundary fails, leaving the system exposed to the very risks the privilege drop was meant to prevent.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-273
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Program does not check return value when invoking functions to drop privileges, which could leave users with higher privileges than expected by forcing those functions to fail.
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Program does not check return value when invoking functions to drop privileges, which could leave users with higher privileges than expected by forcing those functions to fail.
Wie Angreifer es ausnutzen
Angreiferpfad Schritt für Schritt
- 1
Identifiziere einen Codepfad, der nicht vertrauenswürdige Eingaben ohne Validierung verarbeitet.
- 2
Erzeuge eine Payload, die das unsichere Verhalten auslöst — Injection, Traversal, Overflow oder Logik-Missbrauch.
- 3
Liefere die Payload über einen normalen Request aus und beobachte die Reaktion der Anwendung.
- 4
Iteriere, bis die Antwort Daten preisgibt, Angreifer-Code ausführt oder Berechtigungen eskaliert.
Verwundbares Codebeispiel
Vulnerable C++
This code attempts to take on the privileges of a user before creating a file, thus avoiding performing the action with unnecessarily high privileges:
bool DoSecureStuff(HANDLE hPipe) {
bool fDataWritten = false;
ImpersonateNamedPipeClient(hPipe);
HANDLE hFile = CreateFile(...);
/../
RevertToSelf()
/../
} Sicheres Codebeispiel
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.
Präventions-Checkliste
How to prevent CWE-273
- 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.
- Implementation Check the results of all functions that return a value and verify that the value is expected.
- Implementation In Windows, make sure that the process token has the SeImpersonatePrivilege(Microsoft Server 2003). Code that relies on impersonation for security must ensure that the impersonation succeeded, i.e., that a proper privilege demotion happened.
Erkennungssignale
How to detect CWE-273
CWE-273
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.
Häufig gestellte Fragen Was ist CWE-273?
Wie gravierend ist CWE-273?
Welche Sprachen oder Plattformen sind von CWE-273 betroffen?
Wie kann ich CWE-273 verhindern?
Wie erkennt und behebt Plexicus CWE-273?
Wo erfahre ich mehr über CWE-273?
Frequently asked questions
Was ist CWE-273?
This vulnerability occurs when an application tries to lower its system privileges but fails to verify that the operation was successful.
Wie gravierend ist CWE-273?
MITRE stuft die Exploit-Wahrscheinlichkeit als mittel ein — eine Ausnutzung ist realistisch, erfordert aber meist bestimmte Bedingungen.
Welche Sprachen oder Plattformen sind von CWE-273 betroffen?
MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.
Wie kann ich CWE-273 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-273?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-273 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-273?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/273.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
Weaknesses related to CWE-273
CWE-754 Parent
Improper Check for Unusual or Exceptional Conditions
This weakness occurs when software fails to properly anticipate and handle rare or unexpected runtime situations that fall outside normal…
CWE-252 Sibling
Unchecked Return Value
This vulnerability occurs when a program fails to verify the result of a function or method call, allowing it to continue execution…
CWE-253 Sibling
Incorrect Check of Function Return Value
This vulnerability occurs when a program misinterprets or improperly validates the return value from a function, causing it to miss…
CWE-354 Sibling
Improper Validation of Integrity Check Value
This vulnerability occurs when software fails to properly check the integrity of data by validating its checksum or hash value. Without…
CWE-391 Sibling
Unchecked Error Condition
This vulnerability occurs when a program fails to properly check or handle error conditions, such as exceptions or return codes. By…
CWE-394 Sibling
Unexpected Status Code or Return Value
This vulnerability occurs when software fails to properly validate the full range of possible return values from a function or system…
CWE-476 Sibling
NULL Pointer Dereference
This vulnerability occurs when a program attempts to access or manipulate memory using a pointer that is set to NULL, causing a crash or…
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