CVE-2023-46848 in Squid Web Proxy
Summary
by MITRE • 11/03/2023
Squid is vulnerable to Denial of Service, where a remote attacker can perform DoS by sending ftp:// URLs in HTTP Request messages or constructing ftp:// URLs from FTP Native input.
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Analysis
by VulDB Data Team • 09/16/2024
The vulnerability identified as CVE-2023-46848 affects the Squid proxy server, presenting a significant denial of service risk that stems from improper handling of ftp:// URLs within HTTP request messages. This flaw represents a critical security weakness in the proxy server's protocol processing capabilities, where the system fails to adequately validate or sanitize input containing ftp:// scheme identifiers. The vulnerability manifests when the Squid proxy encounters HTTP requests containing ftp:// URLs, either directly embedded in the request or constructed from FTP native input, leading to potential system instability and service disruption. The issue falls under the category of improper input validation and weak protocol handling, which are common attack vectors in proxy server implementations.
The technical implementation of this vulnerability exploits the way Squid processes mixed protocol requests, where HTTP requests containing ftp:// URLs trigger an abnormal processing path that can lead to resource exhaustion or application crashes. When the proxy server attempts to parse or handle these malformed requests, it enters an inconsistent state that prevents normal operation and can cause the service to become unresponsive. This behavior is particularly concerning in high-traffic environments where a single malicious request could potentially bring down the entire proxy service. The flaw demonstrates poor input sanitization practices and inadequate error handling mechanisms within the Squid codebase, allowing attackers to leverage the proxy's legitimate protocol processing capabilities for malicious purposes.
The operational impact of CVE-2023-46848 extends beyond simple service disruption, potentially affecting entire network infrastructures that rely on Squid as a critical component for traffic management and content filtering. Organizations using Squid in production environments face the risk of sustained denial of service attacks that can render their proxy services unavailable for legitimate users, impacting business operations and potentially exposing systems to further exploitation. The vulnerability can be exploited by remote attackers without requiring authentication or specialized privileges, making it particularly dangerous in publicly accessible proxy configurations. Network administrators must consider the potential for cascading failures when this vulnerability is exploited, as proxy service outages can affect multiple downstream systems that depend on proper content filtering and traffic management.
Mitigation strategies for this vulnerability should focus on immediate patching of affected Squid installations, as well as implementing network-level protections such as firewall rules that restrict access to ftp:// URL handling within HTTP requests. Organizations should consider deploying intrusion detection systems that can identify and block suspicious HTTP requests containing ftp:// URLs, while also implementing proper input validation at the network perimeter. The vulnerability aligns with CWE-20, which addresses improper input validation, and represents a specific instance of how protocol confusion can lead to denial of service conditions. From an ATT&CK perspective, this vulnerability maps to techniques involving service denial and protocol manipulation, potentially enabling broader attack campaigns that leverage proxy server weaknesses for network infiltration or disruption. Regular security assessments and monitoring of proxy server logs for unusual patterns involving ftp:// URL processing should be implemented as part of comprehensive security operations to detect potential exploitation attempts.