CVE-2007-4625 in Polipo
Summary
by MITRE
Polipo before 1.0.2 allows remote HTTP servers to cause a denial of service (daemon crash) by aborting the response to a POST request.
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Analysis
by VulDB Data Team • 09/07/2018
The vulnerability identified as CVE-2007-4625 affects the Polipo HTTP proxy software version 1.0.2 and earlier, representing a critical denial of service weakness that can be exploited remotely by malicious HTTP servers. This flaw specifically targets the proxy daemon's handling of POST request responses, creating a scenario where legitimate proxy operations can be disrupted through carefully crafted abortive behaviors from upstream servers. The vulnerability exists within the fundamental request processing logic of the proxy software, where the daemon fails to properly handle abrupt termination of POST request responses, leading to complete service interruption.
The technical implementation of this vulnerability stems from insufficient error handling within Polipo's HTTP response processing module. When a remote HTTP server abruptly terminates a POST request response, the proxy daemon does not implement proper exception handling or resource cleanup procedures. This lack of robust error management causes the daemon to crash and restart, effectively rendering the proxy service unavailable to legitimate users. The flaw operates at the protocol level where the proxy receives incomplete or terminated HTTP responses, particularly during POST operations where data payloads are expected to be transmitted. According to CWE classification, this vulnerability maps to CWE-400: Uncontrolled Resource Consumption, as the daemon consumes excessive resources during the crash and restart cycle, and potentially CWE-640: Weak Password Recovery Mechanism if the proxy is configured to handle authentication flows that could be exploited through this mechanism.
The operational impact of CVE-2007-4625 extends beyond simple service disruption to potentially compromise the availability of network services that depend on the proxy infrastructure. Organizations relying on Polipo for web filtering, caching, or anonymous browsing may experience complete outages when malicious servers exploit this vulnerability. The attack vector requires minimal sophistication as it only necessitates a remote HTTP server to abort a POST request response, making it particularly dangerous in environments where the proxy handles traffic from untrusted sources. This vulnerability aligns with ATT&CK technique T1499.004: Endpoint Denial of Service, where adversaries can cause systems to become unavailable through resource exhaustion or process termination. Network administrators face the challenge of identifying and mitigating this vulnerability without disrupting legitimate proxy operations, as the attack can occur silently in background traffic streams.
Mitigation strategies for this vulnerability primarily focus on immediate software updates to version 1.0.2 or later, where the developers have implemented proper error handling for aborted POST responses. Organizations should also implement network-level controls such as connection timeouts and response validation to detect and prevent malformed responses from causing daemon crashes. Additional protective measures include configuring the proxy to operate in a restricted environment with limited exposure to untrusted HTTP servers, implementing intrusion detection systems to monitor for abnormal daemon restart patterns, and establishing redundant proxy infrastructure to minimize service impact during exploitation attempts. The vulnerability demonstrates the importance of robust error handling in network services and highlights the need for comprehensive testing of edge cases in proxy and gateway software implementations, particularly in scenarios involving incomplete or terminated HTTP transactions.