php-mongodb: The BSON encoder in the MongoDB PHP Driver converts a string length to a 32-bit value without validation

The BSON encoder in the MongoDB PHP Driver converts a string length to a 32-bit value without validation. When an affected application encodes a string near 4 GiB, the allocation size can wrap while the copy operation uses the original length. The resulting heap buffer overflow can corrupt process memory or terminate the PHP process. Reaching this issue requires a non-default runtime configuration that permits multi-gigabyte values. No MongoDB server interaction is required.

Where it's fixed