CVE-2017-0909 in private_address_check Ruby Gem
Summary
by MITRE
The private_address_check ruby gem before 0.4.1 is vulnerable to a bypass due to an incomplete blacklist of common private/local network addresses used to prevent server-side request forgery.
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Analysis
by VulDB Data Team • 01/10/2023
The CVE-2017-0909 vulnerability affects the private_address_check ruby gem version 0.4.0 and earlier, presenting a critical security flaw that undermines server-side request forgery protection mechanisms. This vulnerability stems from an incomplete blacklist implementation that fails to adequately block all private and local network address ranges commonly used in SSRF attacks. The gem was designed to prevent applications from making unauthorized requests to internal network resources, but the flawed blacklist allows attackers to bypass these protections by utilizing address ranges that were not properly accounted for in the validation logic.
The technical flaw resides in the gem's address validation algorithm which relies on a static blacklist of private network ranges. However, this blacklist is incomplete and does not cover all the standard private address spaces defined in rfc 1918 and other networking standards. Attackers can exploit this by crafting requests that target addresses within the overlooked private ranges, effectively bypassing the intended security controls. The vulnerability specifically affects applications that depend on this gem for validating network addresses in HTTP requests, potentially allowing unauthorized access to internal services, databases, or other sensitive resources that should remain isolated from external access.
The operational impact of this vulnerability is significant as it enables attackers to perform server-side request forgery attacks against applications that rely on the private_address_check gem for protection. An attacker could potentially access internal systems, perform reconnaissance on internal networks, or exploit other vulnerabilities within the internal infrastructure. This bypass allows for unauthorized data access, privilege escalation, and potential lateral movement within network environments where applications are expected to be protected from internal network requests. The vulnerability is particularly dangerous in cloud environments or applications that handle sensitive data, as it could lead to complete compromise of internal systems.
Mitigation strategies for CVE-2017-0909 involve upgrading to version 0.4.1 or later of the private_address_check gem, which includes a comprehensive blacklist of private network addresses. Organizations should also implement additional layers of protection such as network segmentation, firewall rules, and proper input validation at multiple levels of their applications. The fix addresses the incomplete blacklist by incorporating all standard private address ranges and ensuring proper validation of network addresses. Security teams should conduct thorough testing of their applications after implementing the update to verify that the SSRF protection is functioning correctly and that no other vulnerabilities remain in their network access controls. This vulnerability aligns with CWE-917 weakness in secure coding practices related to improper neutralization of special elements used in an expression, and represents a typical ATT&CK technique for initial access through server-side request forgery attacks.