CVE-2021-20215 in Privoxy
Summary
by MITRE • 03/25/2021
A flaw was found in Privoxy in versions before 3.0.29. Memory leaks in the show-status CGI handler when memory allocations fail can lead to a system crash.
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Analysis
by VulDB Data Team • 04/05/2021
The vulnerability identified as CVE-2021-20215 resides within the Privoxy web proxy software, specifically affecting versions prior to 3.0.29. This issue manifests as a memory leak condition within the show-status CGI handler component of the application. The flaw represents a critical security concern that can potentially lead to system instability and denial of service conditions when the software encounters memory allocation failures during normal operation. Privoxy serves as a non-caching web proxy that filters web content and provides privacy protection, making it a critical component in many network security infrastructures where its stability directly impacts overall system reliability.
The technical implementation of this vulnerability stems from inadequate memory management practices within the show-status CGI handler functionality. When the application attempts to allocate memory for processing status information and encounters allocation failures, the system fails to properly release previously allocated memory resources. This memory leak condition accumulates over time, eventually exhausting available system memory resources and leading to application crashes or system instability. The vulnerability specifically affects the CGI (Common Gateway Interface) handler responsible for displaying system status information, which is accessed through web-based interfaces that administrators and users employ to monitor proxy operations. This flaw demonstrates poor error handling and resource management practices that are consistent with CWE-401, which identifies improper management of memory allocation and deallocation as a fundamental weakness in software systems.
The operational impact of CVE-2021-20215 extends beyond simple system crashes to encompass broader network security implications. When Privoxy becomes unstable due to memory exhaustion, it can disrupt web browsing activities for all users relying on the proxy service, potentially creating denial of service conditions that affect business operations and user productivity. Organizations that depend on Privoxy for content filtering, privacy protection, and web traffic management face significant risks when this vulnerability is exploited, particularly in environments where continuous availability is critical. The vulnerability can be exploited by malicious actors who intentionally trigger memory allocation failures through crafted requests to the show-status CGI endpoint, leading to repeated memory leaks that eventually cause system crashes. This makes the vulnerability particularly dangerous in production environments where Privoxy serves as a core infrastructure component.
Mitigation strategies for CVE-2021-20215 focus primarily on immediate version upgrades to Privoxy 3.0.29 or later, which contain the necessary patches to address the memory leak conditions. System administrators should conduct comprehensive vulnerability assessments to identify all instances of affected Privoxy versions within their networks and prioritize patching operations accordingly. Network monitoring solutions should be enhanced to detect unusual memory consumption patterns that may indicate the onset of memory leak conditions, providing early warning capabilities before complete system crashes occur. Additionally, implementing proper resource limits and monitoring for memory usage can help contain the impact of any remaining vulnerabilities while patches are deployed. From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, as the memory leak conditions can result in service disruption that impacts network availability. Organizations should also consider implementing intrusion detection systems that can identify attempts to access the vulnerable show-status CGI handler endpoint, providing additional layers of defense against exploitation attempts.