CVE-2016-10725 in Bitcoin Core
Summary
by MITRE
In Bitcoin Core before v0.13.0, a non-final alert is able to block the special "final alert" (which is supposed to override all other alerts) because operations occur in the wrong order. This behavior occurs in the remote network alert system (deprecated since Q1 2016). This affects other uses of the codebase, such as Bitcoin Knots before v0.13.0.knots20160814 and many altcoins.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 02/25/2020
The vulnerability described in CVE-2016-10725 represents a critical flaw in the Bitcoin Core cryptocurrency implementation that stems from improper ordering of operations within the alert system. This issue affects versions prior to v0.13.0 and demonstrates a fundamental failure in the logical sequence of alert processing that allows malicious actors to disrupt the network's ability to receive critical security notifications. The problem specifically manifests in the remote network alert system which was officially deprecated in the first quarter of 2016, yet remained functional in older codebases and continued to be inherited by various cryptocurrency implementations. The flaw creates a scenario where a non-final alert can effectively prevent the delivery of the final alert, which is designed to override all other alerts and serves as the ultimate mechanism for network-wide security notifications.
The technical implementation of this vulnerability resides in the improper execution order of alert processing operations within the Bitcoin Core codebase. When the system processes alerts, it fails to properly prioritize the final alert over non-final alerts, creating a race condition or logical flaw in the alert handling sequence. This ordering issue is classified under CWE-691, which specifically addresses insufficient control flow management where the sequence of operations does not properly account for critical precedence requirements. The vulnerability allows an attacker to craft a non-final alert that, due to the incorrect processing order, prevents subsequent final alerts from being properly recognized or executed, thereby undermining the entire alert system's security posture. This represents a classic example of how improper control flow management can lead to complete system subversion, particularly in security-critical applications where the order of operations directly impacts system integrity.
The operational impact of this vulnerability extends far beyond the immediate Bitcoin Core implementation, as it affects numerous derivative projects and alternative cryptocurrency implementations. Bitcoin Knots, which is a fork of Bitcoin Core, was similarly vulnerable until its v0.13.0.knots20160814 release, demonstrating how this flaw propagated through the cryptocurrency ecosystem. Many altcoins that inherited code from Bitcoin Core also carried this vulnerability, creating a widespread security risk across the cryptocurrency landscape. From an operational security perspective, this vulnerability could enable attackers to prevent critical security notifications from reaching network participants, potentially allowing malicious actors to exploit other vulnerabilities without warning the community. The attack pattern aligns with ATT&CK technique T1070.004, which involves the use of deception and manipulation of information flow to prevent detection or response to security incidents. This flaw essentially creates a backdoor mechanism where the intended security override functionality is neutralized, making it impossible for legitimate final alerts to function as designed.
The mitigation strategy for this vulnerability required a complete overhaul of the alert processing logic within Bitcoin Core and its derivative implementations. The fix involved reordering the operations to ensure that final alerts are processed with absolute precedence over non-final alerts, eliminating the possibility that malicious actors could block critical notifications. This fix was implemented in Bitcoin Core v0.13.0 and subsequently propagated to other affected implementations. Organizations using vulnerable versions were strongly advised to upgrade immediately, as the vulnerability could be exploited to prevent the delivery of security patches, network updates, or critical incident notifications. The remediation process also required careful code auditing of alert handling systems across all affected implementations, ensuring that similar ordering issues did not exist in other security-critical code paths. Additionally, the deprecation of the remote alert system in Q1 2016 and its eventual removal in subsequent versions provided a permanent solution, though the vulnerability highlighted the importance of proper control flow management in security-critical applications. The incident underscored the need for comprehensive testing of security-critical code paths, particularly those involving precedence and ordering requirements that could be exploited by attackers.