CVE-2025-14764 identifies a cryptographic vulnerability in the Amazon S3 Encryption Client for Go, specifically related to the absence of cryptographic key commitment in the encryption process. The vulnerability arises when encrypted data keys (EDKs) are stored in an "instruction file" rather than embedded in S3 metadata records. In this scenario, a user with write access to the S3 bucket can introduce a malicious EDK that decrypts to different plaintext than intended, effectively allowing data tampering without detection. This issue is categorized under CWE-327, indicating the use of a broken or risky cryptographic algorithm or mechanism. The lack of key commitment means the client cannot verify that the encrypted data key corresponds to the original plaintext key, enabling substitution attacks. The vulnerability has a CVSS 3.1 base score of 5.3, reflecting medium severity, with attack vector as network, attack complexity high, privileges required low, no user interaction, and impact limited to integrity compromise. There is no known exploit in the wild as of the publication date. AWS recommends upgrading to version 4.0 or later of the S3 Encryption Client for Go to mitigate this issue. This fix likely includes proper cryptographic key commitment mechanisms to ensure the integrity of encrypted data keys regardless of storage method. Organizations using older versions and storing EDKs in instruction files are at risk of undetected data manipulation, which can have downstream effects on data reliability and trustworthiness.

For European organizations, this vulnerability primarily threatens data integrity within cloud storage environments using the vulnerable AWS S3 Encryption Client for Go. Attackers with write access to S3 buckets could manipulate encrypted data keys to cause decryption to altered plaintext, potentially corrupting critical data or injecting malicious content without detection. This undermines trust in encrypted data and can disrupt business operations relying on data accuracy, such as financial records, healthcare information, or intellectual property. Although confidentiality is not directly impacted, the integrity breach can lead to compliance violations under GDPR and other data protection regulations, especially if altered data leads to incorrect decisions or disclosures. The medium severity and requirement for write access limit the attack surface but do not eliminate risk, particularly in multi-tenant or shared environments where write permissions may be more broadly granted. Organizations with automated data processing pipelines or compliance auditing relying on encrypted data integrity are especially vulnerable. The absence of known exploits provides a window for proactive mitigation, but the risk remains significant given the potential for stealthy data tampering.

European organizations should immediately upgrade the Amazon S3 Encryption Client for Go to version 4.0 or later to ensure cryptographic key commitment is properly implemented. Review and audit S3 bucket permissions to minimize write access, especially for users or services that do not require it, employing the principle of least privilege. Avoid storing encrypted data keys in instruction files where possible; prefer embedding EDKs in S3 metadata records as recommended by AWS best practices. Implement monitoring and alerting for unusual write activities or modifications to instruction files within S3 buckets. Conduct integrity checks and validation of decrypted data where feasible to detect tampering early. Incorporate cryptographic best practices and regularly update encryption libraries to stay protected against emerging vulnerabilities. Additionally, document and test incident response procedures for potential data integrity incidents related to cloud storage. Engage with AWS support or security advisories for ongoing updates and patches related to this vulnerability. Finally, ensure compliance teams are aware of the risk to address regulatory implications proactively.