CVE-2025-14761 is a cryptographic vulnerability identified in the AWS SDK for PHP, specifically related to the handling of encrypted data keys (EDKs) used in S3 bucket encryption workflows. The vulnerability stems from the absence of a cryptographic key commitment mechanism when EDKs are stored in an "instruction file" rather than embedded in S3 metadata. This missing commitment allows an attacker with write access to the S3 bucket to replace or introduce a new EDK that decrypts to altered plaintext, effectively enabling data integrity manipulation without detection. The cryptographic weakness falls under CWE-327, indicating the use of a broken or risky cryptographic algorithm or scheme. Exploitation requires the attacker to have write permissions on the S3 bucket, which is a low privilege level but the attack complexity is high due to the need to craft valid EDKs that bypass integrity checks. The vulnerability does not affect confidentiality or availability directly but compromises data integrity, which can have significant downstream effects on application behavior and trustworthiness of stored data. AWS has released a fix in SDK version 3.368.0 that introduces proper cryptographic key commitment to prevent this attack vector. No known exploits have been reported in the wild, but the vulnerability's presence in a widely used SDK component poses a latent risk. Organizations using the AWS SDK for PHP for S3 encryption should upgrade promptly and review their access controls and encryption key management policies to mitigate potential exploitation.

For European organizations, this vulnerability primarily threatens data integrity within cloud storage environments using AWS SDK for PHP with S3 encryption. Attackers with write access to S3 buckets could manipulate encrypted data keys to alter decrypted content, potentially leading to corrupted data, unauthorized data modifications, or application malfunctions relying on the integrity of stored data. This could impact sectors handling sensitive or regulated data, such as finance, healthcare, and government, where data integrity is critical for compliance and operational trust. Although confidentiality and availability are not directly impacted, the integrity compromise could lead to indirect consequences like erroneous decision-making, data loss through corrupted backups, or reputational damage. The medium CVSS score reflects moderate risk, but the widespread use of AWS services in Europe and the criticality of cloud infrastructure elevate the importance of addressing this vulnerability promptly. Organizations with lax S3 bucket permissions or legacy SDK versions are at higher risk. The absence of known exploits suggests a window for proactive mitigation before active attacks emerge.

1. Upgrade the AWS SDK for PHP to version 3.368.0 or later immediately to incorporate the cryptographic key commitment fix. 2. Audit and tighten S3 bucket permissions to enforce the principle of least privilege, ensuring only trusted users and services have write access. 3. Implement monitoring and alerting on S3 bucket write operations to detect unusual or unauthorized changes to encryption-related files, including instruction files. 4. Review and enhance encryption key management policies, including key rotation and validation procedures, to detect anomalies in encrypted data keys. 5. Conduct regular security assessments and penetration testing focused on cloud storage encryption workflows to identify potential weaknesses. 6. Educate development and operations teams about secure usage of AWS SDKs and the importance of applying security patches promptly. 7. Consider using AWS CloudTrail and AWS Config rules to track and enforce compliance with encryption and access control policies. 8. If feasible, implement additional cryptographic integrity checks at the application layer to detect tampering beyond SDK-level protections.