CVE-2007-4098 in Tor
Summary
by MITRE
Tor before 0.1.2.15 does not properly distinguish "streamids from different exits," which might allow remote attackers with control over Tor routers to inject cells into arbitrary streams.
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Analysis
by VulDB Data Team • 09/06/2018
The vulnerability described in CVE-2007-4098 represents a critical flaw in the Tor anonymity network's stream management mechanism that existed prior to version 0.1.2.15. This weakness stems from insufficient differentiation between stream identifiers originating from various exit nodes within the Tor network, creating a fundamental security gap that could be exploited by malicious actors who control Tor routers. The issue specifically affects the way Tor handles stream identification and cell routing between relay nodes, potentially allowing attackers to manipulate network traffic flows.
The technical flaw manifests in the improper handling of streamids within Tor's circuit management system, where the network fails to adequately distinguish between streams that originate from different exit relays. This lack of proper streamid differentiation creates a scenario where an attacker controlling one or more Tor routers could potentially inject network cells into arbitrary streams, effectively enabling traffic manipulation and potential data injection attacks. The vulnerability exploits the underlying assumption that streamids are unique across all connections, when in reality they may be reused or confused between different exit points.
Operationally, this vulnerability poses significant risks to Tor users' anonymity and network integrity. Attackers with control over Tor routers could potentially perform stream injection attacks that compromise the confidentiality and integrity of communications passing through the Tor network. The impact extends beyond simple data injection to potentially enable more sophisticated attacks such as traffic correlation, where malicious actors could monitor and analyze network flows to de-anonymize users. This weakness undermines the fundamental security model of Tor, which relies on proper stream isolation to protect user privacy and prevent traffic analysis attacks.
The vulnerability aligns with CWE-284, which addresses improper access control mechanisms in software systems, and relates to ATT&CK technique T1566, specifically targeting credential access through network infrastructure manipulation. Organizations and users should implement immediate mitigations including upgrading to Tor version 0.1.2.15 or later, which includes proper streamid differentiation mechanisms. Additional protective measures involve monitoring for suspicious router behavior, implementing network segmentation, and ensuring that Tor clients and relays operate with proper security configurations. The fix addresses the core issue by implementing robust streamid management that prevents cross-contamination between streams from different exit nodes, thereby restoring proper isolation and preventing unauthorized cell injection attacks.