CVE-2025-53359 is a medium-severity vulnerability identified in the rust-ethereum project's ethereum crate versions prior to 0.18.0. The vulnerability relates to improper handling of signature malleability checks across different Ethereum transaction types. Specifically, the crate only enforced signature malleability checks, as defined by Ethereum Improvement Proposal 2 (EIP-2), for legacy transactions but failed to apply these checks to newer transaction types introduced by EIP-2930, EIP-1559, and EIP-7702. Signature malleability refers to the possibility of altering the digital signature of a transaction without invalidating it, which can lead to multiple valid signatures for the same transaction data. While signature malleability itself is not inherently a security flaw, the lack of consistent checks across all transaction types represents a deviation from the Ethereum specification and can introduce risks in multi-implementation blockchain environments where different clients might interpret transactions differently. This inconsistency could potentially be exploited to cause transaction replay, double-spending, or confusion in transaction validation processes. The vulnerability does not require authentication, user interaction, or privileges to exploit and affects all users of the ethereum crate versions below 0.18.0. The issue has been addressed in version 0.18.0 by extending signature malleability checks to all transaction types. Until upgrading, users can implement manual checks for transaction malleability outside the crate as a workaround. No known exploits are currently reported in the wild.

For European organizations involved in blockchain development, cryptocurrency exchanges, DeFi platforms, or any services relying on the rust-ethereum crate for transaction processing, this vulnerability could undermine transaction integrity and trustworthiness. In multi-client or multi-implementation blockchain environments, inconsistent signature validation might lead to transaction replay attacks or discrepancies in transaction acceptance, potentially resulting in financial losses or operational disruptions. Although the vulnerability does not directly compromise confidentiality or availability, it impacts the integrity of transaction processing, which is critical for financial and contractual operations. Organizations using the affected crate in production environments risk transaction malleability issues that could complicate auditing, compliance, and dispute resolution. Given the growing adoption of Ethereum-based solutions in Europe, especially in fintech hubs and blockchain innovation centers, the impact could be significant if unpatched. However, the absence of known exploits and the medium CVSS score suggest the threat is moderate but warrants prompt attention.

The primary mitigation is to upgrade the ethereum crate to version 0.18.0 or later, where the signature malleability checks are correctly implemented for all transaction types. For organizations unable to upgrade immediately, implementing manual signature malleability checks for EIP-2930, EIP-1559, and EIP-7702 transactions outside the crate is recommended to ensure compliance with EIP-2 standards. Additionally, organizations should audit their blockchain transaction validation processes to detect any anomalies caused by signature malleability. Integrating comprehensive transaction monitoring and anomaly detection tools can help identify suspicious transaction patterns indicative of malleability exploitation. It is also advisable to review and test all dependent systems and smart contracts interacting with the ethereum crate to ensure they handle transaction signatures consistently. Finally, maintaining up-to-date dependency management and incorporating security testing in the development lifecycle will reduce exposure to similar specification deviations.