S3 Encryption Client for PHP is an open-source client-side encryption library used to facilitate writing and reading encrypted records to S3. When the encrypted data key (EDK) is stored in an "Instruction File" instead of S3's metadata record, the EDK is exposed to an "Invisible Salamanders" attack (https://eprint.iacr.org/2019/016), which could allow the EDK to be replaced with a new key.
AWS SDK for PHP is the Amazon Web Services software development kit for PHP. Within the scope of requests to S3 object keys and/or prefixes containing a Unix double-dot, a URI path traversal is possible. The issue exists in the buildEndpoint method in the RestSerializer component of the AWS SDK for PHP v3 prior to 3.288.1. The buildEndpoint method relies on the Guzzle Psr7 UriResolver utility, which strips dot segments …
There's an improper default directory umask that can potentially allow unauthorized modifications of PHP code.