CVE-2026-51269 in ESP32-audioI2S
Summary
by MITRE • 07/28/2026
schreibfaul1 ESP32-audioI2S 3.4.5 has a heap-based buffer overflow vulnerability in the connecttospeech() function. The application accepts attacker-controlled long speech text input, performs URL encoding, and directly appends the encoded result into a fixed ps_ptr heap buffer when constructing HTTP TTS request headers. Lack of input length validation and boundary checking allows remote attackers to craft oversized input to trigger out-of-bounds heap write, resulting in arbitrary code execution.
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Analysis
by VulDB Data Team • 07/28/2026
The schreibfaul1 ESP32-audioI2S library version 3.4.5 contains a critical heap-based buffer overflow vulnerability within its connecttospeech() function that presents significant security implications for embedded audio applications. This vulnerability stems from inadequate input validation mechanisms when processing attacker-controlled speech text data, creating an avenue for remote code execution through carefully crafted malicious inputs. The flaw specifically manifests during the construction of HTTP Text-to-Speech request headers where the application performs URL encoding on user-supplied text and subsequently appends this encoded data directly into a fixed-size heap buffer without proper length verification.
The technical exploitation of this vulnerability occurs when an attacker provides excessively long speech text input that, after URL encoding, exceeds the predetermined buffer size allocated for the ps_ptr heap buffer. This buffer overflow condition results in out-of-bounds memory writes that can overwrite adjacent heap memory regions, potentially corrupting critical program data structures or executable code segments. The absence of boundary checking and input length validation creates a deterministic path for attackers to manipulate memory layout and gain unauthorized control over the device's execution flow. The vulnerability is particularly concerning given the ESP32 platform's widespread use in IoT applications where these devices often operate with minimal security oversight.
From an operational perspective, this vulnerability represents a severe risk to embedded audio systems that rely on the ESP32-audioI2S library for speech synthesis capabilities. Remote attackers can exploit this flaw to execute arbitrary code on affected devices without requiring physical access or authentication credentials, potentially leading to complete system compromise. The heap-based nature of the overflow means that the attack vector can be particularly stealthy, as memory corruption may not immediately manifest as system crashes but instead allow for gradual exploitation and persistent access to vulnerable systems.
Security mitigation strategies should focus on implementing proper input validation mechanisms with strict length limits for speech text inputs before URL encoding and buffer operations. Developers should employ dynamic buffer allocation techniques or implement comprehensive boundary checking procedures that validate all input lengths against predetermined buffer sizes. Additionally, the application should incorporate heap integrity checking mechanisms and consider using secure coding practices such as those recommended by the CWE (Common Weakness Enumeration) guidelines for buffer overflow prevention. The ATT&CK framework categorizes this vulnerability under the 'Memory Exhaustion' and 'Command and Scripting Interpreter' techniques, highlighting the need for both defensive programming practices and runtime monitoring to detect potential exploitation attempts. Organizations utilizing this library should prioritize immediate patching or mitigation implementation to protect their embedded systems from remote code execution attacks that could compromise entire IoT networks.