Bref enable serverless PHP on AWS Lambda. When Bref is used with the Event-Driven Function runtime and the handler is a `RequestHandlerInterface`, then the Lambda event is converted to a PSR7 object. During the conversion process, if the request is a MultiPart, each part is parsed and its content added in the `$files` or `$parsedBody` arrays. The conversion process produces a different output compared to the one of plain PHP when keys ending with and open square bracket ([) are used. Based on the application logic the difference in the body parsing might lead to vulnerabilities and/or undefined behaviors. This vulnerability is patched in 2.1.13.

Affected: Packagist: bref/bref

## Impacted Resources

bref/src/Event/Http/Psr7Bridge.php:130-168

## Description

When Bref is used with the Event-Driven Function runtime and the handler is a `RequestHandlerInterface`, then the Lambda event is converted to a PSR7 object. During the conversion process, if the request is a MultiPart, each part is parsed and its content added in the `$files` or `$parsedBody` arrays. To do that, the following method is called with as first argument the result array (`$files` or `$parsedBody`), as second argument the part name, and as third argument the part content:

```php /** * Parse a string key like "files[id_cards][jpg][]" and do $array['files']['id_cards']['jpg'][] = $value */ private static function parseKeyAndInsertValueInArray(array &$array, string $key, mixed $value): void { if (! str_contains($key, '[')) { $array[$key] = $value;

return; }

$parts = explode('[', $key); // files[id_cards][jpg][] => [ 'files', 'id_cards]', 'jpg]', ']' ] $pointer = &$array;

foreach ($parts as $k => $part) { if ($k === 0) { $pointer = &$pointer[$part];

continue; }

// Skip two special cases: // [[ in the key produces empty string // [test : starts with [ but does not end with ] if ($part === '' || ! str_ends_with($part, ']')) { // Malformed key, we use it "as is" $array[$key] = $value;

return; }

$part = substr($part, 0, -…