Buffer Overflow in schreibfaul1 ESP32-audioI2S

Executive Summary

This is a heap-based buffer overflow in the schreibfaul1 ESP32-audioI2S library version 3.4.5. The vulnerability occurs in the connecttospeech() function where user-controlled speech text is URL-encoded and appended to a fixed-size heap buffer without proper length validation. Excessively long input causes the encoded payload to exceed the buffer's capacity, leading to memory corruption during HTTP request construction for Text-to-Speech API calls.

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Detection Guidance

To detect this vulnerability, monitor for heap buffer overflow errors during HTTP request processing for Text-to-Speech (TTS) API calls. Use AddressSanitizer-enabled ESP32 builds to detect heap overflow errors during TTS request processing. Check for crashes or watchdog reboots when processing oversized speech input parameters.

• Enable AddressSanitizer in ESP32 builds to detect heap buffer overflows during TTS API calls.

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Impact Analysis

An attacker can send a malicious network request with oversized speech input to trigger a heap buffer overflow. This may cause a remote denial of service by forcing an ESP32 watchdog reboot or freezing the network audio service. In some cases, it could lead to arbitrary code execution within the device's application privilege scope or leak sensitive internal data like heap runtime and audio processing details.

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Mitigation Strategies

Immediately restrict input length for speech text parameters to a safe maximum size before URL encoding. Validate and sanitize all user-controlled input to prevent oversized payloads. Disable or isolate the Text-to-Speech (TTS) service if not essential. Monitor network traffic for unusually large HTTP requests targeting the TTS endpoint.

• Apply input length restrictions and validation to speech text parameters before processing.

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