CVE-2016-1254 in Tor
Summary
by MITRE
Tor before 0.2.8.12 might allow remote attackers to cause a denial of service (client crash) via a crafted hidden service descriptor.
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Analysis
by VulDB Data Team • 01/17/2023
The vulnerability identified as CVE-2016-1254 affects the Tor anonymity network version 0.2.8.11 and earlier, presenting a significant security risk that could lead to denial of service conditions. This flaw specifically targets the client-side processing of hidden service descriptors, which are critical components in Tor's architecture for maintaining anonymous communication channels. The vulnerability arises from insufficient input validation within the Tor client's handling of these descriptors, creating a potential attack vector for remote adversaries seeking to disrupt Tor services.
The technical implementation of this vulnerability stems from a buffer overflow condition that occurs when the Tor client processes malformed hidden service descriptors. When a crafted descriptor is received, the client fails to properly validate the descriptor's structure and content, leading to memory corruption that ultimately results in application crash. This type of vulnerability falls under CWE-121, which describes heap-based buffer overflow conditions, and represents a classic example of improper input validation in network protocols. The flaw exists in the descriptor parsing logic where the client assumes certain data structures will conform to expected formats without adequate bounds checking.
The operational impact of CVE-2016-1254 extends beyond simple service disruption, as it can be exploited to systematically target Tor clients and potentially undermine the network's reliability. Attackers can craft malicious descriptors that, when processed by vulnerable clients, cause immediate crashes and require manual intervention to restore normal operation. This vulnerability particularly affects users who are actively participating in the Tor network as clients, making it a significant concern for both individual users and organizations that rely on Tor for privacy protection. The attack surface is broad since any user who encounters a malicious descriptor during normal network operation could be affected, potentially leading to cascading failures in network connectivity and anonymity services.
Mitigation strategies for this vulnerability require immediate software updates to version 0.2.8.12 or later, which contains the necessary patches to properly validate hidden service descriptors. Network administrators should implement monitoring systems to detect unusual client crash patterns that might indicate exploitation attempts. The fix addresses the core issue through enhanced input validation and proper memory management practices that prevent buffer overflows during descriptor processing. This remediation aligns with ATT&CK technique T1499.004, which covers network disruption attacks, and represents a fundamental security improvement in protocol implementation. Organizations should also consider implementing network segmentation and access controls to limit exposure while updates are deployed, ensuring that the Tor network's integrity remains intact during the remediation process.