CVE-2025-9960 in is-localhost-ip
Summary
by MITRE • 09/22/2025
A restriction bypass vulnerability in is-localhost-ip could allow attackers to perform Server-Side Request Forgery (SSRF). This issue affects is-localhost-ip: 2.0.0.
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Analysis
by VulDB Data Team • 09/24/2025
The vulnerability identified as CVE-2025-9960 represents a critical security flaw in the is-localhost-ip npm package version 2.0.0, specifically manifesting as a restriction bypass that enables Server-Side Request Forgery attacks. This package is commonly utilized in web applications and server-side environments to validate whether an IP address corresponds to a localhost address, making it a crucial component in security-sensitive operations that require IP address validation. The flaw occurs within the package's validation logic where it fails to properly enforce restrictions on IP address validation, creating a pathway for malicious actors to bypass intended security controls.
The technical implementation of this vulnerability stems from insufficient input validation and improper handling of edge cases within the is-localhost-ip package. When applications utilize this package for IP address validation, particularly in contexts where localhost access should be restricted or controlled, the vulnerability allows attackers to craft requests that appear to target localhost resources while actually redirecting to arbitrary external endpoints. This bypass mechanism operates by exploiting how the package processes specific IP address formats or validation scenarios, enabling attackers to circumvent security controls that rely on the package's accurate localhost detection. The flaw essentially allows an attacker to manipulate the validation logic to accept non-localhost IP addresses as valid localhost addresses, creating a false positive condition that opens doors for SSRF exploitation.
From an operational impact perspective, this vulnerability poses significant risks to organizations that depend on the is-localhost-ip package for security controls in their applications. The SSRF capability enabled by this bypass can lead to various attack vectors including internal network scanning, access to internal services that should remain isolated, data exfiltration from internal systems, and potential escalation to more severe vulnerabilities within the network infrastructure. Attackers can leverage this vulnerability to probe internal services that are typically protected by firewall rules or network segmentation, potentially exposing sensitive systems, databases, or administrative interfaces that should only be accessible from localhost. The impact extends beyond immediate data exposure to include potential system compromise and lateral movement within network environments where internal services are not properly secured.
Organizations should immediately assess their dependency on the affected is-localhost-ip package version 2.0.0 and implement remediation measures to address this vulnerability. The primary mitigation strategy involves upgrading to a patched version of the package where the restriction bypass has been resolved through improved input validation and more robust IP address handling mechanisms. Security teams should also implement additional layers of protection including network segmentation, firewall rules that restrict outbound connections from application servers, and comprehensive monitoring of unusual network requests that may indicate SSRF attempts. The vulnerability aligns with CWE-284 Access Control Issues and can be categorized under ATT&CK technique T1190 for Proxy Relay and T1046 for Network Service Scanning, emphasizing the need for both defensive measures and active monitoring to detect potential exploitation attempts. Organizations should also consider implementing web application firewalls and validating all external inputs to prevent exploitation of similar validation bypass vulnerabilities in their application stacks.