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CWE-163 Variant Incomplete
Improper Neutralization of Multiple Trailing Special Elements
This vulnerability occurs when software accepts external input but fails to properly sanitize or incorrectly handles multiple trailing special characters or elements. When this unsanitized data is…
Definition
What is CWE-163?
This vulnerability occurs when software accepts external input but fails to properly sanitize or incorrectly handles multiple trailing special characters or elements. When this unsanitized data is passed to another system component, these elements can be interpreted in harmful, unintended ways.
During data processing, trailing special elements like repeated slashes, dots, or escape sequences can trick parsers or handlers. If an application doesn't clean up these multiple trailing elements, it can cause the downstream component to misinterpret boundaries, change execution paths, or trigger unexpected actions, creating a security flaw.
For developers, this means input validation must account for sequences of special characters at the end of data strings, not just single instances. Robust sanitization should collapse or remove illegitimate trailing element repetitions before data is forwarded, preventing manipulation of file paths, command arguments, or protocol directives.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-163
-
Directory listings in web server using multiple trailing slash
-
Multiple trailing dot allows directory listing
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 pseudo
MITRE hat kein Codebeispiel für diese CWE veröffentlicht. Das untenstehende Muster ist illustrativ — kanonische Referenzen findest du unter Ressourcen.
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
// Untrusted input flows directly into the sensitive sink.
return executeUnsafe(input);
} 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-163
- Developers should anticipate that multiple trailing special elements will be injected/removed/manipulated in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system.
- Implementation Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- Implementation While it is risky to use dynamically-generated query strings, code, or commands that mix control and data together, sometimes it may be unavoidable. Properly quote arguments and escape any special characters within those arguments. The most conservative approach is to escape or filter all characters that do not pass an extremely strict allowlist (such as everything that is not alphanumeric or white space). If some special characters are still needed, such as white space, wrap each argument in quotes after the escaping/filtering step. Be careful of argument injection (CWE-88).
- Implementation Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
Erkennungssignale
How to detect CWE-163
Führe dynamische Application-Security-Tests gegen den Live-Endpoint aus.
Beobachte Runtime-Logs auf ungewöhnliche Exception-Traces, fehlerhafte Eingaben oder Versuche, Autorisierung zu umgehen.
Code Review: Markiere jeden neuen Code, der Eingaben von dieser Oberfläche ohne validierte Framework-Helper verarbeitet.
Plexicus erkennt CWE-163 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-163?
Wie gravierend ist CWE-163?
Welche Sprachen oder Plattformen sind von CWE-163 betroffen?
Wie kann ich CWE-163 verhindern?
Wie erkennt und behebt Plexicus CWE-163?
Wo erfahre ich mehr über CWE-163?
Frequently asked questions
Was ist CWE-163?
This vulnerability occurs when software accepts external input but fails to properly sanitize or incorrectly handles multiple trailing special characters or elements. When this unsanitized data is passed to another system component, these elements can be interpreted in harmful, unintended ways.
Wie gravierend ist CWE-163?
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-163 betroffen?
MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.
Wie kann ich CWE-163 verhindern?
Developers should anticipate that multiple trailing special elements will be injected/removed/manipulated in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system. Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform…
Wie erkennt und behebt Plexicus CWE-163?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-163 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-163?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/163.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
Weaknesses related to CWE-163
CWE-162 Parent
Improper Neutralization of Trailing Special Elements
This vulnerability occurs when an application fails to properly sanitize or remove trailing special characters from user-supplied input…
CWE-42 Sibling
Path Equivalence: 'filename.' (Trailing Dot)
This vulnerability occurs when a system accepts file or directory paths that end with a dot (like 'file.txt.' or 'folder.') without…
CWE-46 Sibling
Path Equivalence: 'filename ' (Trailing Space)
This vulnerability occurs when an application processes file paths that end with a space character (like 'document.txt ') without properly…
CWE-49 Sibling
Path Equivalence: 'filename/' (Trailing Slash)
This vulnerability occurs when an application accepts file or directory paths that end with a slash (e.g., 'documents/') without properly…
CWE-54 Sibling
Path Equivalence: 'filedir\' (Trailing Backslash)
This vulnerability occurs when an application accepts file or directory paths that end with a backslash (like 'filedir\') without properly…
CWE-43 Child
Path Equivalence: 'filename....' (Multiple Trailing Dot)
This vulnerability occurs when an application accepts file or directory paths containing multiple trailing dots (like 'file....') without…
CWE-52 Child
Path Equivalence: '/multiple/trailing/slash//'
This vulnerability occurs when an application accepts file or directory paths containing multiple consecutive forward slashes (like…
Ressourcen
Further reading
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