CVE-2020-8450 in Web Proxy
Summary
by MITRE
An issue was discovered in Squid before 4.10. Due to incorrect buffer management, a remote client can cause a buffer overflow in a Squid instance acting as a reverse proxy.
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Analysis
by VulDB Data Team • 03/28/2024
The vulnerability identified as CVE-2020-8450 represents a critical buffer overflow flaw within the Squid caching proxy software version 4.9 and earlier. This issue specifically affects Squid instances configured as reverse proxies, where the software serves as an intermediary between client requests and backend servers. The vulnerability stems from inadequate buffer management practices during the processing of HTTP requests, creating a scenario where malicious input can exceed allocated memory boundaries and overwrite adjacent memory regions. The flaw occurs when Squid processes certain malformed HTTP headers or request data that triggers improper memory allocation and handling within the proxy's request parsing logic.
The technical exploitation of this vulnerability involves a remote attacker who can craft malicious HTTP requests designed to trigger the buffer overflow condition. When Squid processes these requests as a reverse proxy, the flawed buffer management causes memory corruption that can lead to arbitrary code execution or service disruption. The vulnerability is particularly dangerous because it allows remote attackers to exploit the system without requiring authentication, making it a significant threat to organizations relying on Squid for their web proxy services. The buffer overflow occurs in the HTTP request handling component of Squid, where insufficient bounds checking allows data to be written beyond the allocated buffer space, potentially overwriting critical program variables or return addresses.
The operational impact of CVE-2020-8450 extends beyond immediate service availability concerns to encompass potential system compromise and data integrity violations. Organizations using vulnerable Squid instances as reverse proxies face risks of unauthorized access, data exfiltration, and denial of service attacks. The vulnerability affects the core functionality of the proxy service, potentially allowing attackers to bypass security controls, redirect traffic, or gain elevated privileges on the affected system. This issue particularly impacts web applications that rely on Squid for caching, load balancing, or security filtering, as the compromise of the proxy can affect all traffic passing through it. The vulnerability also creates opportunities for attackers to establish persistent access points within network infrastructure, as the compromised proxy can serve as a foothold for further attacks.
Organizations should prioritize immediate mitigation through patch management, upgrading to Squid version 4.10 or later where the buffer overflow has been resolved. The fix addresses the underlying buffer management issues by implementing proper bounds checking and memory allocation practices that prevent data from exceeding allocated buffer boundaries. Network segmentation and monitoring should be enhanced to detect anomalous traffic patterns that might indicate exploitation attempts. Additionally, implementing intrusion detection systems that can identify malformed HTTP requests and deploying web application firewalls can provide additional layers of protection. This vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and maps to ATT&CK technique T1071.004 for application layer protocol tunneling, as attackers could leverage this flaw to establish covert communication channels through the compromised proxy infrastructure.