CVE-2025-14763 identifies a cryptographic vulnerability in the AWS S3 Encryption Client for Java, specifically related to the use of a broken or risky cryptographic algorithm (CWE-327). The root cause is the absence of cryptographic key commitment when the encrypted data key (EDK) is stored in an "instruction file" instead of the standard S3 metadata record. Key commitment is a cryptographic technique that binds the ciphertext to the key, preventing substitution attacks. Without this, an attacker with write access to the S3 bucket can replace the EDK with a malicious one that decrypts to different plaintext than intended. This attack vector compromises data integrity by allowing undetected tampering with encrypted data. The vulnerability requires the attacker to have write permissions on the S3 bucket but does not require user interaction or elevated privileges beyond that. The CVSS 3.1 score is 5.3 (medium), reflecting the moderate impact on integrity and the complexity of exploitation. AWS has released version 4.0.0 of the S3 Encryption Client for Java to address this issue by implementing proper cryptographic key commitment. No known exploits are currently reported in the wild, but the vulnerability poses a risk to organizations relying on client-side encryption with this library. The flaw highlights the importance of cryptographic best practices in client-side encryption implementations, especially in cloud storage contexts where data integrity is critical.

For European organizations, this vulnerability primarily threatens the integrity of encrypted data stored in AWS S3 buckets when using the vulnerable Java encryption client. An attacker with write access to the bucket could manipulate encrypted data without detection, potentially leading to corrupted or malicious data being processed by applications. This could disrupt business operations, cause data reliability issues, and undermine trust in data security. While confidentiality and availability are not directly affected, the integrity compromise could have downstream effects, including compliance violations under GDPR if data tampering leads to inaccurate personal data processing. Organizations relying heavily on AWS S3 for sensitive or regulated data storage and using the affected client version are at higher risk. The medium severity rating suggests that while the threat is not critical, it warrants timely remediation to prevent exploitation.

European organizations should immediately upgrade the AWS S3 Encryption Client for Java to version 4.0.0 or later, which includes the fix for this vulnerability by implementing cryptographic key commitment. Additionally, organizations should audit S3 bucket permissions to ensure that write access is strictly limited to trusted users and services, minimizing the risk of malicious EDK injection. Implement monitoring and alerting on S3 bucket write activities to detect unusual or unauthorized modifications. Review and validate encryption workflows to confirm that encrypted data keys are stored securely and not in instruction files unless properly protected. Conduct regular security assessments of client-side encryption implementations to verify adherence to cryptographic best practices. Finally, maintain an inventory of all applications and services using the vulnerable client to ensure comprehensive patching.