CVE-2007-4096 in Tor
Summary
by MITRE
Buffer overflow in Tor before 0.1.2.15, when using BSD natd support, allows remote attackers to cause a denial of service via unspecified vectors.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 09/06/2018
The vulnerability identified as CVE-2007-4096 represents a critical buffer overflow condition within the Tor anonymity network software prior to version 0.1.2.15. This flaw specifically manifests when the software utilizes BSD natd support functionality, creating a potential attack surface that remote adversaries can exploit to disrupt service availability. The buffer overflow occurs in the handling of network traffic when Tor operates in conjunction with BSD's network address translation daemon, which is commonly used in FreeBSD and other BSD-based operating systems. This particular configuration creates a scenario where malformed input data can exceed the bounds of allocated memory buffers, potentially leading to unpredictable behavior and system instability.
The technical implementation of this vulnerability stems from inadequate input validation and memory management within Tor's network processing routines when interfacing with BSD natd. When Tor receives network packets that trigger the natd integration, the software fails to properly bounds-check data structures, allowing attackers to craft specially formatted network traffic that overflows predetermined buffer allocations. This condition can be exploited through various network-based attack vectors that manipulate the data flow between Tor clients and relay nodes. The vulnerability does not appear to enable arbitrary code execution but rather focuses on causing denial of service conditions that can render Tor services unavailable to legitimate users. The flaw operates at the application layer of the network stack, specifically affecting the packet processing and routing mechanisms that are fundamental to Tor's operation as a privacy-enhancing network.
The operational impact of CVE-2007-4096 extends beyond simple service disruption to potentially compromising the integrity of the Tor network itself. When exploited, this vulnerability can cause Tor processes to crash or become unresponsive, effectively removing nodes from the network and reducing overall anonymity network capacity. The attack vector is particularly concerning because it targets the core functionality of Tor's network infrastructure rather than just user-facing components. Network administrators and security professionals must consider that attackers could leverage this vulnerability to systematically degrade Tor services across multiple nodes, potentially leading to widespread network disruption. The vulnerability affects the availability aspect of the CIA triad, specifically targeting the denial of service component that can make legitimate network services inaccessible. This represents a significant concern for users who rely on Tor for privacy and security, as network degradation can force users to seek alternative anonymity solutions or expose their communications to surveillance.
Mitigation strategies for this vulnerability involve immediate software updates to versions 0.1.2.15 and later, which contain patches addressing the buffer overflow conditions in BSD natd integration. System administrators should also implement network monitoring to detect anomalous traffic patterns that might indicate exploitation attempts. The fix typically involves implementing proper input validation and bounds checking within the affected code paths, ensuring that all data received from network interfaces is properly sanitized before processing. Organizations should consider disabling BSD natd support in Tor configurations when it is not required, as this reduces the attack surface. Additionally, implementing intrusion detection systems that monitor for unusual network behavior can help identify potential exploitation attempts. This vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and maps to ATT&CK technique T1499.004 for network denial of service attacks. The remediation process should include comprehensive testing to ensure that the patch does not introduce regressions in network functionality while maintaining the intended security protections.