CVE-2025-14763 is a cryptographic vulnerability classified under CWE-327, identified in the Amazon S3 Encryption Client for Java. 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 used, preventing substitution attacks. Without this, an attacker with write permissions to the S3 bucket can replace the EDK with a malicious one that decrypts to different plaintext than originally intended. This undermines the integrity of the encrypted data, allowing undetected tampering or substitution of data. The vulnerability does not expose plaintext directly, so confidentiality is not compromised. The CVSS v3.1 score is 5.3 (medium), reflecting the moderate impact and the requirement for low privileges and network access but no user interaction. The vulnerability affects all versions prior to 4.0.0 of the S3 Encryption Client for Java. AWS recommends upgrading to version 4.0.0 or later, which includes the necessary cryptographic key commitment to prevent this attack vector. No known exploits are reported in the wild as of the publication date. This vulnerability is particularly relevant for organizations that rely on client-side encryption using this AWS SDK component and store encrypted data keys in instruction files, a less common but supported configuration.

For European organizations, the primary impact is on data integrity within cloud storage environments using the vulnerable S3 Encryption Client for Java. An attacker with write access to the S3 bucket can manipulate encrypted data keys to cause decryption to incorrect plaintext, potentially leading to data corruption, application errors, or unauthorized data manipulation without detection. This could disrupt business operations, damage trust in data authenticity, and complicate compliance with data integrity requirements under regulations such as GDPR. Since confidentiality and availability are not directly affected, the risk is focused on integrity. Organizations with multi-tenant cloud environments or those that grant write access to multiple users or services are at higher risk. The vulnerability could also be leveraged as part of a broader attack chain to undermine data reliability or to inject malicious data payloads. The medium severity rating suggests that while the threat is significant, it requires specific conditions and privileges to exploit, limiting its scope somewhat.

1. Upgrade the Amazon S3 Encryption Client for Java to version 4.0.0 or later immediately to ensure cryptographic key commitment is enforced. 2. Audit and restrict write permissions on S3 buckets to the minimum necessary users and services, reducing the risk of unauthorized EDK substitution. 3. Review encryption configurations to avoid storing encrypted data keys in instruction files unless absolutely necessary; prefer storing EDKs in S3 metadata records where possible. 4. Implement monitoring and alerting on unusual write activities to S3 buckets, especially changes to encryption-related files or instruction files. 5. Conduct integrity checks on encrypted data and keys regularly to detect tampering early. 6. Educate developers and DevOps teams about secure usage of AWS encryption SDKs and the importance of applying security patches promptly. 7. Incorporate cryptographic best practices and key management policies that include key commitment verification in encryption workflows. 8. Engage with AWS support or security teams for guidance on secure client-side encryption implementations and to stay informed about any emerging threats or patches.