CVE-2026-48486 in Signum Node
Summary
by MITRE • 09/03/2026
Signum Node is a HDD-mined cryptocurrency using an energy efficient and fair Proof-of-Commitment (PoC+) consensus algorithm. Prior to version 3.9.9, an integer overflow in BlockServiceImpl.applyBlock() allowed a miner to receive an arbitrarily inflated block reward by crafting a block with a negative totalFeeCashBackNqt value. The vulnerability was introduced when the SMART_FEES hardfork (block ~1,029,000) enabled fee cash-back and burn accounting without overflow protection. This issue has been patched in version 3.9.9.
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Analysis
by VulDB Data Team • 09/03/2026
The Signum Node blockchain architecture relies on a Proof-of-Commitment consensus mechanism that prioritizes energy efficiency and fairness through HDD mining operations. A critical security flaw was identified within the core block processing logic, specifically residing in the BlockServiceImpl.applyBlock() method prior to version 3.9.9 of the software. This vulnerability stems from an integer overflow condition that occurs during the calculation of transaction fees and their subsequent distribution mechanisms. The root cause is traced back to the implementation of the SMART_FEES hardfork at block height approximately one million two hundred ninety thousand, which introduced fee cash-back features and burn accounting protocols without implementing adequate boundary checks or arithmetic safeguards against negative value representation in signed integer variables.
From a technical perspective, the vulnerability allows an attacker who controls mining hardware to craft malicious blocks containing transaction data that results in a negative totalFeeCashBackNqt value due to underflow conditions inherent in fixed-width integer types such as int32 or int64 depending on the specific implementation details of the underlying Java Virtual Machine environment. When this malformed block is processed by network nodes, the arithmetic operation intended to distribute fees fails to clamp the result within valid positive ranges. Instead, the negative value propagates through the reward calculation logic, effectively subtracting from the base block reward in a manner that mathematically results in an arbitrarily inflated final payout for the miner submitting the malicious block. This exploitation bypasses the economic constraints designed into the consensus algorithm, allowing the attacker to mint coins at rates far exceeding protocol limits without corresponding proof of work or stake commitment.
The operational impact of this vulnerability is severe as it directly compromises the integrity and security model of the cryptocurrency network. By enabling arbitrary inflation of block rewards, an active miner could potentially deplete the total coin supply faster than intended, leading to rapid hyperinflation within the circulating token economy. This undermines trust in the fixed monetary policy typically associated with such digital assets and can cause significant depreciation in market value for legitimate holders. Furthermore, successful exploitation allows a single entity or colluding group of miners to gain disproportionate influence over network governance decisions that rely on voting power tied to coin holdings, thereby centralizing control contrary to the decentralized ethos of the platform. The flaw also poses risks to node operators who might inadvertently accept invalid blocks if their software versions are not updated promptly, potentially causing chain splits or consensus failures across parts of the network.
This vulnerability aligns with Common Weakness Enumeration category CWE-190 which defines integer overflow and wraparound errors that lead to unexpected behavior when arithmetic operations exceed variable capacity limits. In terms of adversarial tactics, this exploitation technique corresponds to ATT&CK techniques related to resource hijacking or economic manipulation within blockchain environments where consensus rules are subverted for financial gain. The mitigation strategy implemented in version 3.9.9 involves rigorous input validation and the use of safe arithmetic libraries that prevent underflow by checking bounds before performing subtraction operations on fee values. Network participants must upgrade their node software immediately to patch this flaw, ensuring that all nodes enforce strict positive value constraints during block verification processes. Additionally, implementing formal verification methods for critical consensus logic in future hardforks can help detect similar logical flaws before deployment into production environments.