CVE-2012-4684 in Bitcoin-Qt
Summary
by MITRE
The alert functionality in bitcoind and Bitcoin-Qt before 0.7.0 supports different character representations of the same signature data, but relies on a hash of this signature, which allows remote attackers to cause a denial of service (resource consumption) via a valid modified signature for a circulating alert.
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Analysis
by VulDB Data Team • 02/25/2019
The vulnerability identified as CVE-2012-4684 resides within the alert system of bitcoind and Bitcoin-Qt client software versions prior to 0.7.0. This issue stems from a fundamental flaw in how the software handles signature validation for network alerts, creating a potential vector for resource exhaustion attacks that could disrupt the entire Bitcoin network's operational integrity. The vulnerability operates at the protocol level where alert messages are processed, making it particularly dangerous as it affects the core communication mechanisms that maintain network consensus and security.
The technical root cause of this vulnerability lies in the inconsistent handling of character representations within signature data. Specifically, the system accepts multiple valid character encodings for the same underlying signature data while simultaneously relying on a hash function to validate these signatures. This design creates a scenario where attackers can generate modified but valid signatures that appear identical to the system's hash verification process, yet consume significantly more computational resources during processing. The flaw essentially allows for signature collision through character representation manipulation, where different character sequences produce the same hash output but require different processing cycles to validate.
The operational impact of this vulnerability extends beyond simple denial of service to potentially compromise the entire Bitcoin network's stability and security infrastructure. Remote attackers can exploit this weakness by crafting modified alert signatures that consume excessive CPU and memory resources during validation, leading to resource exhaustion that can affect node performance and potentially cause network-wide disruptions. This type of attack specifically targets the alert propagation mechanism that was designed to broadcast critical security notices and network updates, making it a particularly effective vector for network disruption. The vulnerability creates a resource consumption attack pattern that aligns with common denial of service strategies, where legitimate network traffic is disrupted through excessive resource utilization.
This vulnerability maps directly to CWE-129 and CWE-131 categories within the Common Weakness Enumeration system, specifically addressing issues related to input validation and resource management. The attack vector follows patterns consistent with ATT&CK technique T1499.004 for network denial of service, where adversaries manipulate system resources through crafted inputs. The flaw demonstrates a classic example of how cryptographic systems can be undermined through improper handling of data representation rather than weaknesses in the cryptographic algorithms themselves. Security practitioners should note that this vulnerability represents a critical design flaw in the alert system architecture that could be exploited to create cascading failures within the Bitcoin network's distributed validation system.
Mitigation strategies for CVE-2012-4684 require immediate deployment of Bitcoin-Qt version 0.7.0 or later, which addresses the signature validation inconsistency through improved character representation handling and more robust hash verification processes. Network operators should implement additional monitoring for unusual resource consumption patterns during alert processing and consider rate limiting for alert message validation. The fix implemented in version 0.7.0 involves strengthening the signature validation algorithm to ensure consistent character handling regardless of representation variations, thereby preventing the resource exhaustion attack vector. Organizations should also conduct comprehensive security assessments of their Bitcoin node configurations to ensure all systems are updated and that proper network segmentation is implemented to limit potential attack impact.