CVE-2024-29186

Technical Description

Bref is an open-source project that helps users go serverless on Amazon Web Services with PHP. When Bref prior to version 2.1.17 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. In the parsing process, the `Content-Type` header of each part is read using the `Riverline/multipart-parser` library.

The library, in the `StreamedPart::parseHeaderContent` function, performs slow multi-byte string operations on the header value.

Precisely, the `mb_convert_encoding` function is used with the first (`$string`) and third (`$from_encoding`) parameters read from the header value.

An attacker could send specifically crafted requests which would force the server into performing long operations with a consequent long billed duration.

The attack has the following requirements and limitations: The Lambda should use the E

Remediation

Check the references section for vendor advisories and patches from mnapoli. Update bref to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected Products

References