Buffer Overread in SSL_select_next_proto May Lead to Loss of Confidentiality

CVE-2024-5535

Summary

A buffer overread vulnerability exists in OpenSSL that may lead to the accidental exposure of up to 255 bytes of sensitive memory content when the API function SSL_select_next_proto is called with an empty list of supported client protocols. This situation is unlikely to arise under normal circumstances, as it typically requires a configuration or programming mistake. When SSL_select_next_proto is invoked incorrectly, it fails to detect this and can return invalid memory content, potentially leading to a loss of confidentiality. Primarily, this affects applications using Next Protocol Negotiation (NPN), which is less common than the more widely adopted Application Layer Protocol Negotiation (ALPN). Developers must ensure proper handling of protocol lists to avoid inadvertently exposing private data.

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