CVE-2020-7670 in agoo
Summary
by MITRE
agoo through 2.12.3 allows request smuggling attacks where agoo is used as a backend and a frontend proxy also being vulnerable. It is possible to conduct HTTP request smuggling attacks by sending the Content-Length header twice. Furthermore, invalid Transfer Encoding headers were found to be parsed as valid which could be leveraged for TE:CL smuggling attacks.
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Analysis
by VulDB Data Team • 06/11/2020
The vulnerability identified as CVE-2020-7670 affects the agoo web server software version 2.12.3 and earlier, presenting a significant security risk when the software operates as a backend server in proxy configurations. This flaw enables malicious actors to exploit HTTP request smuggling techniques, particularly when agoo is deployed behind vulnerable frontend proxies. The vulnerability stems from improper handling of HTTP headers, specifically the Content-Length and Transfer-Encoding fields, which creates opportunities for attackers to manipulate request processing and potentially gain unauthorized access to backend systems or bypass security controls.
The technical implementation of this vulnerability involves the agoo server's inadequate validation and processing of HTTP headers, allowing duplicate Content-Length headers to be accepted and processed. This behavior creates a fundamental flaw in the HTTP request parsing mechanism that can be exploited by attackers to manipulate how requests are interpreted by both the frontend proxy and backend server. The vulnerability also permits invalid Transfer-Encoding headers to be treated as valid, which expands the attack surface significantly. This dual vulnerability creates conditions for both CL:TE and TE:CL smuggling attacks, where attackers can craft requests that appear legitimate to the frontend proxy but are interpreted differently by the backend server, leading to potential data leakage or unauthorized access.
The operational impact of CVE-2020-7670 extends beyond simple request manipulation, as it can enable attackers to perform sophisticated attacks that compromise the integrity of the entire proxy chain. When agoo is used as a backend server, attackers can exploit this vulnerability to inject malicious requests that bypass authentication mechanisms, access restricted resources, or perform actions on behalf of legitimate users. The vulnerability is particularly dangerous in environments where agoo serves as a backend component in larger web architectures, as it can provide attackers with a foothold to escalate privileges or conduct more extensive attacks against the underlying infrastructure. This weakness aligns with CWE-444, which addresses improper handling of HTTP requests, and represents a critical security gap in web application security.
Organizations using agoo in proxy configurations must implement immediate mitigations to prevent exploitation of this vulnerability. The primary recommendation involves upgrading to agoo version 2.12.4 or later, which contains patches addressing the header parsing issues. Additionally, network administrators should implement strict HTTP header validation at proxy levels, ensuring that duplicate headers are rejected and that Transfer-Encoding headers undergo rigorous validation before processing. Security teams should also consider implementing monitoring solutions that can detect anomalous header patterns or unusual request behaviors that may indicate exploitation attempts. The vulnerability demonstrates the importance of proper HTTP protocol implementation and highlights the critical need for security-conscious development practices. Organizations should follow ATT&CK technique T1071.004 for application layer protocol manipulation and T1566 for credential access through web application attacks, as these frameworks provide guidance for defending against such exploitation patterns.