CVE-2025-14761 identifies a cryptographic vulnerability in the AWS SDK for PHP, specifically in its client-side encryption library used for encrypting and decrypting records stored in Amazon S3. The root cause is the absence of cryptographic key commitment when encrypted data keys (EDKs) are stored in an "instruction file" instead of the S3 object's metadata. 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, effectively allowing undetected tampering with encrypted data. This vulnerability impacts the integrity of encrypted data but does not compromise confidentiality or availability. The CVSS v3.1 score is 5.3 (medium), reflecting the need for low privileges (write access to the bucket), network attack vector, and no user interaction, but with a higher attack complexity. AWS has fixed this issue in SDK for PHP version 3.368.0 and later. Organizations using earlier versions for client-side encryption with S3 should upgrade to prevent potential data integrity violations. No known exploits have been reported in the wild as of now.

For European organizations, this vulnerability primarily threatens the integrity of encrypted data stored in Amazon S3 when using the AWS SDK for PHP for client-side encryption. Attackers with write access to the S3 bucket could substitute encrypted data keys, causing decryption to yield altered plaintext without detection. This could lead to data corruption, unauthorized data manipulation, or injection of malicious content, potentially impacting business operations, compliance with data integrity regulations (such as GDPR), and trust in cloud storage solutions. Since confidentiality and availability are not directly affected, the risk is focused on data integrity and the reliability of encrypted data. Organizations relying on client-side encryption for sensitive or regulated data in S3 should consider this a significant risk. The requirement for write access to the S3 bucket means that internal threat actors or compromised credentials pose the greatest risk. The absence of known exploits reduces immediate urgency but does not eliminate the threat, especially in environments with lax access controls.

1. Upgrade the AWS SDK for PHP to version 3.368.0 or later immediately to ensure the cryptographic key commitment is properly implemented. 2. Review and tighten S3 bucket permissions to restrict write access only to trusted users and services, minimizing the risk of unauthorized EDK substitution. 3. Implement monitoring and alerting on S3 bucket write activities, especially changes to instruction files or metadata related to encrypted objects. 4. Conduct audits of existing encrypted data to detect any anomalies or signs of tampering that could indicate exploitation. 5. Educate development and DevOps teams about secure usage of client-side encryption libraries and the importance of keeping SDKs up to date. 6. Consider additional cryptographic integrity checks at the application level to detect unauthorized modifications to encrypted data. 7. Regularly review AWS security best practices and compliance requirements related to encryption and key management.