CVE-2011-2778 in Tor
Summary
by MITRE
Multiple heap-based buffer overflows in Tor before 0.2.2.35 allow remote attackers to cause a denial of service (memory corruption) or possibly execute arbitrary code by (1) establishing a SOCKS connection to SocksPort or (2) leveraging a SOCKS proxy configuration.
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Analysis
by VulDB Data Team • 03/20/2021
The vulnerability described in CVE-2011-2778 represents a critical heap-based buffer overflow issue affecting the Tor anonymization network software prior to version 0.2.2.35. This flaw exists within the SOCKS proxy implementation and presents significant security risks to users who rely on Tor for anonymous communication. The vulnerability specifically targets memory management functions within the Tor client that handle SOCKS protocol connections, creating opportunities for remote attackers to manipulate heap memory structures through crafted network requests.
The technical exploitation of this vulnerability occurs through two primary attack vectors that leverage the SOCKS proxy functionality. The first vector involves establishing a direct SOCKS connection to the SocksPort, while the second vector utilizes SOCKS proxy configuration parameters that are processed by the Tor client. Both attack paths result in heap memory corruption when the software attempts to handle malformed or oversized data packets during SOCKS protocol negotiations. The buffer overflow occurs because the Tor implementation fails to properly validate input lengths when processing SOCKS connection requests, leading to memory corruption that can manifest as program crashes or potentially arbitrary code execution.
From an operational perspective, this vulnerability poses severe risks to Tor users and network integrity. The potential for remote code execution means that attackers could gain control of systems running vulnerable Tor clients, making this particularly dangerous for users who depend on Tor for privacy and security. The denial of service aspect alone could be leveraged to disrupt Tor network operations and compromise the anonymity services that users rely upon. Network administrators and security professionals must understand that this vulnerability affects not just individual user systems but could potentially impact the broader Tor network infrastructure and user base.
The vulnerability aligns with CWE-121, heap-based buffer overflow, and demonstrates characteristics consistent with ATT&CK technique T1071.004 for application layer protocol manipulation. The attack surface is particularly concerning because SOCKS proxy functionality is fundamental to Tor's operation, making this vulnerability difficult to avoid and potentially affecting a large number of users. The exploitation requires minimal privileges and can be executed remotely, making it an attractive target for malicious actors seeking to compromise Tor users' systems. Organizations and individuals using Tor software should prioritize immediate patching to address this vulnerability, as the potential for both service disruption and code execution makes this a critical security concern.
Mitigation strategies should include immediate deployment of Tor version 0.2.2.35 or later, which contains the necessary patches to address the heap overflow conditions. Network monitoring should be enhanced to detect unusual SOCKS connection patterns that might indicate exploitation attempts. Security teams should also consider implementing network segmentation and access controls to limit potential attack surfaces for Tor client installations. Regular security assessments of Tor deployments are recommended to ensure continued protection against similar vulnerabilities. The patching process should be prioritized in environments where Tor is used for sensitive communications, as the risk of exploitation increases with the number of exposed Tor client instances.