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-201 Base Draft
Insertion of Sensitive Information Into Sent Data
This vulnerability occurs when an application sends data to an external party, but accidentally includes sensitive information—like passwords, keys, or personal data—that the recipient should not be…
Definition
What is CWE-201?
This vulnerability occurs when an application sends data to an external party, but accidentally includes sensitive information—like passwords, keys, or personal data—that the recipient should not be able to access.
This flaw often happens because of overly broad data selection or logging mechanisms that package more information than necessary for a given transaction. For example, an API response might return an entire user object, including internal fields like hashed passwords or security questions, instead of just the needed profile data. Developers should carefully review all data payloads sent to clients, third-party services, or logs, ensuring they follow the principle of least privilege and expose only what is explicitly required.
Catching these leaks manually is challenging, as sensitive data can be buried deep in nested objects or only appear under specific conditions. While SAST tools can flag patterns of data exposure, Plexicus uses AI to analyze data flows in context and suggest precise code fixes—such as implementing stricter output filters or using data sanitization libraries—saving hours of manual review and reducing the risk of accidental disclosure across your entire application stack.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-201
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Collaboration platform does not clear team emails in a response, allowing leak of email addresses
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 SQL
The following is an actual MySQL error statement:
Warning: mysql_pconnect(): Access denied for user: 'root@localhost' (Using password: N1nj4) in /usr/local/www/wi-data/includes/database.inc on line 4 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-201
- Requirements Specify which data in the software should be regarded as sensitive. Consider which types of users should have access to which types of data.
- Implementation Ensure that any possibly sensitive data specified in the requirements is verified with designers to ensure that it is either a calculated risk or mitigated elsewhere. Any information that is not necessary to the functionality should be removed in order to lower both the overhead and the possibility of security sensitive data being sent.
- System Configuration Setup default error messages so that unexpected errors do not disclose sensitive information.
- 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.
Erkennungssignale
How to detect CWE-201
Plexicus erkennt CWE-201 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.
Häufig gestellte Fragen Was ist CWE-201?
Wie gravierend ist CWE-201?
Welche Sprachen oder Plattformen sind von CWE-201 betroffen?
Wie kann ich CWE-201 verhindern?
Wie erkennt und behebt Plexicus CWE-201?
Wo erfahre ich mehr über CWE-201?
Frequently asked questions
Was ist CWE-201?
This vulnerability occurs when an application sends data to an external party, but accidentally includes sensitive information—like passwords, keys, or personal data—that the recipient should not be able to access.
Wie gravierend ist CWE-201?
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-201 betroffen?
MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.
Wie kann ich CWE-201 verhindern?
Specify which data in the software should be regarded as sensitive. Consider which types of users should have access to which types of data. Ensure that any possibly sensitive data specified in the requirements is verified with designers to ensure that it is either a calculated risk or mitigated elsewhere. Any information that is not necessary to the functionality should be removed in order to lower both the overhead and the possibility of security sensitive data being sent.
Wie erkennt und behebt Plexicus CWE-201?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-201 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-201?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/201.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
Weaknesses related to CWE-201
CWE-200 Parent
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-1258 Sibling
Exposure of Sensitive System Information Due to Uncleared Debug Information
This vulnerability occurs when hardware fails to erase sensitive data like cryptographic keys and intermediate values before entering…
CWE-1273 Sibling
Device Unlock Credential Sharing
This vulnerability occurs when the secret keys or passwords required to unlock a device's hidden features are shared between multiple…
CWE-1295 Sibling
Debug Messages Revealing Unnecessary Information
The product's debug messages or logs expose excessive internal system details, potentially revealing sensitive information that could aid…
CWE-1431 Sibling
Driving Intermediate Cryptographic State/Results to Hardware Module Outputs
This vulnerability occurs when a hardware cryptographic module leaks sensitive internal data through its output channels. Instead of only…
CWE-203 Sibling
Observable Discrepancy
This vulnerability occurs when an application responds differently to unauthorized users based on internal conditions. Attackers can…
CWE-209 Sibling
Generation of Error Message Containing Sensitive Information
This vulnerability occurs when an application reveals sensitive details about its internal systems, user data, or environment within error…
CWE-213 Sibling
Exposure of Sensitive Information Due to Incompatible Policies
This vulnerability occurs when a system's data handling aligns with the developer's security rules but accidentally reveals information…
CWE-215 Sibling
Insertion of Sensitive Information Into Debugging Code
This vulnerability occurs when developers embed sensitive data, such as passwords or API keys, within debugging statements like logs or…
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