OpenResty URI Parameters Access Restriction Bypass Vulnerability [CVE-2018-9230]
A vulnerability in OpenResty could allow an unauthenticated, remote attacker to bypass access restrictions on an affected system.
The vulnerability is due to improper validation of URI parameter values by the affected software when handling the ngx.req.get_uri_args and ngx.req.get_post_args functions with more than 100 parameters. An attacker could exploit this vulnerability by using GET and POST requests that contain more than 100 parameters in the affected functions, where malicious input is included in parameters after the first 100. A successful exploit could allow the attacker to cause a URI parameter overflow and bypass restrictions on the system.
Proof-of-concept code that demonstrates an exploit of this vulnerability is publicly available.
OpenResty Inc. has confirmed the vulnerability and released software updates.
CVE Number – CVE-2018-9230
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To exploit this vulnerability, an attacker must send GET and POST requests to the affected system, which may require access to trusted, internal networks. This access limitation reduces the likelihood of a successful exploit.
The vulnerability affects certain Web Application Firewall (WAF) products running an affected version of OpenResty.
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Administrators are advised to apply the appropriate updates.
Administrators are advised to allow only trusted users to have network access.
Administrators can help protect affected systems from external attacks by using a solid firewall strategy.
Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.
Administrators are advised to monitor affected systems.
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OpenResty Inc. a security report at the following link: Bypass007 – Uri parameter overflow in Openresty.md
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OpenResty Inc. has released software updates at the following link: OpenResty 1.13.6.1
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Duncan is a technology professional with over 20 years experience of working in various IT roles. He has a interest in cyber security, and has a wide range of other skills in radio, electronics and telecommunications.