Details
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Software: WP-Ban
Version: 1.62
Homepage: http://wordpress.org/plugins/wp-ban/
Advisory report: https://security.dxw.com/advisories/vulnerability-in-wp-ban-allows-visitors-to-bypass-the-ip-blacklist-in-some-configurations/
CVE: CVE-2014-6230
CVSS: 5 (Medium; AV:N/AC:L/Au:N/C:P/I:N/A:N)

Description
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Vulnerability in WP-Ban allows visitors to bypass the IP blacklist in some configurations

Vulnerability
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This plugin allows blacklisting users based on their IP address, however it takes the IP address from the X-Forwarded-For header if available.
Not all Web server configurations will strip or replace X-Forwarded-For headers – in which case the IP ban can be bypassed by sending this header. This plugin therefore only works in certain configurations, but does not warn admins of this fact.

Proof of concept
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Visit http://localhost/wp-admin/admin.php?page=wp-ban/ban-options.php
Set “Banned IPs” to “127.0.0.1″
Execute “curl http://localhost/\" and see the “You Are Banned” message
Execute “curl http://localhost/ -H \'X-Forwarded-For: 999.999.999.999\'\" and see that it displays the page

Note that this will not work if your Web server sets or strips X-Forwarded-For headers.
(To remove the IP blacklist run this SQL: “delete from wp_options where option_name=\'banned_ips\';\")

Mitigations
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Upgrade to version 1.6.4 or later.
If a reverse-proxy is used, check the “I am using a reverse proxy” box in the plugin settings, and ensure that X-Forwarded-For headers are being set even if the request already contains an X-Forwarded-For header.

Disclosure policy
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dxw believes in responsible disclosure. Your attention is drawn to our disclosure policy: https://security.dxw.com/disclosure/

Please contact us on security@dxw.com to acknowledge this report if you received it via a third party (for example, plugins@wordpress.org) as they generally cannot communicate with us on your behalf.

This vulnerability will be published if we do not receive a response to this report with 14 days.

Timeline
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2014-08-27: Discovered
2014-09-04: Reported to vendor by email
2014-09-04: Requested CVE
2014-09-04: Vendor responded
2014-09-17: Vendor reported a fixed version released
2014-09-17: Published



Discovered by dxw:
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Tom Adams
Please visit security.dxw.com for more information.