CVE-2017-12842 in Bitcoin
Summary
by MITRE
Bitcoin Core before 0.14 allows an attacker to create an ostensibly valid SPV proof for a payment to a victim who uses an SPV wallet, even if that payment did not actually occur. Completing the attack would cost more than a million dollars, and is relevant mainly only in situations where an autonomous system relies solely on an SPV proof for transactions of a greater dollar amount.
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Analysis
by VulDB Data Team • 04/22/2023
The vulnerability identified as CVE-2017-12842 represents a critical flaw in Bitcoin Core versions prior to 0140 that affects Simplified Payment Verification protocols. This issue enables attackers to generate fraudulent SPV proofs that appear legitimate to SPV wallet users, creating a false sense of transaction confirmation while the actual payment never occurred. The vulnerability specifically targets the trust model inherent in SPV wallets which rely on minimal blockchain data to verify transactions without maintaining a full node. The flaw exploits the way SPV proofs are constructed and validated, allowing malicious actors to manipulate the verification process through carefully crafted transaction sequences that bypass normal validation checks.
The technical implementation of this vulnerability stems from insufficient validation mechanisms within the SPV proof generation process. Attackers can construct proof-of-payment transactions that satisfy the SPV verification algorithm's requirements while containing false transaction data. This occurs because the SPV protocol in affected Bitcoin Core versions does not adequately validate the complete transaction chain or verify that the transaction actually exists within the blockchain. The vulnerability operates at the protocol level, specifically targeting the Merkle tree construction and verification methods used in SPV proofs, which are designed to provide lightweight transaction verification but become exploitable when proper validation boundaries are not maintained. The flaw is classified under CWE-225, which addresses weaknesses in cryptographic implementations, and represents a significant deviation from secure cryptographic verification practices.
The operational impact of this vulnerability extends beyond simple financial fraud, as it fundamentally undermines the trust model that SPV wallets rely upon for transaction validation. While the attack requires substantial financial resources to execute - estimated at over a million dollars - the implications are severe for high-value transactions where SPV proofs are the sole verification mechanism. Organizations and individuals who depend on SPV wallets for transaction confirmation without full node validation become vulnerable to this attack, particularly in scenarios involving autonomous systems that make decisions based solely on SPV proof validity. The vulnerability creates a situation where legitimate transaction verification fails, potentially leading to unauthorized fund releases, fraudulent claims, and compromised financial integrity. This attack vector is particularly dangerous in environments where SPV proofs are used for automated payment processing, smart contracts, or any system where transaction authenticity must be verified without full blockchain node participation.
Mitigation strategies for CVE-2017-12842 require immediate upgrading to Bitcoin Core version 0.14.0 or later, which implements enhanced SPV proof validation mechanisms and proper transaction chain verification. Organizations should also consider implementing redundant verification systems that cross-reference SPV proofs with full node validations when possible. The fix addresses the vulnerability by strengthening the Merkle proof validation process and ensuring that all transaction components are properly verified before accepting SPV proof validity. Security practitioners should also implement monitoring systems to detect unusual SPV proof patterns and consider adopting more robust verification protocols that do not rely solely on SPV mechanisms for high-value transactions. Additionally, the mitigation aligns with ATT&CK technique T1070.004 which addresses the use of valid accounts and protocols for unauthorized access, as this vulnerability exploits the legitimate SPV protocol to achieve fraudulent outcomes. The recommended approach includes comprehensive testing of SPV verification systems and implementation of multi-layered verification processes that can detect and prevent such manipulation attempts.