CVE-2026-51254 in ESP32-audioI2S
Summary
by MITRE • 07/28/2026
schreibfaul1 ESP32-audioI2S v3.4.5 has an integer underflow vulnerability in the MP3Decoder::GetBits() function of the MP3 decoder due to unchecked bit reading operations. The lack of validation on the nBits parameter causes the cachedBits counter to underflow to negative values, leading to invalid bit manipulation, incorrect bitstream parsing, application crash, or arbitrary code execution via a specially crafted MP3 file.
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Analysis
by VulDB Data Team • 07/28/2026
The schreibfaul1 ESP32-audioI2S library version 3.4.5 contains a critical integer underflow vulnerability within its MP3 decoder implementation that poses significant security risks to embedded audio applications. This vulnerability specifically affects the MP3Decoder::GetBits() function where the nBits parameter controlling bit reading operations lacks proper validation, creating a dangerous condition that can be exploited by malicious actors. The flaw resides in the fundamental bitstream parsing logic of the MP3 decoder component, which is designed to process compressed audio data for playback on ESP32 microcontroller platforms.
The technical implementation of this vulnerability stems from unchecked bit manipulation operations within the MP3 decoding pipeline where the cachedBits counter variable becomes vulnerable to underflow conditions. When an attacker provides a specially crafted MP3 file with maliciously constructed bitstream data, the nBits parameter can cause the internal counter to decrement beyond zero into negative territory. This integer underflow creates unpredictable behavior in the bit reading mechanism that fundamentally breaks the decoder's ability to properly parse audio data. The vulnerability operates at the core of the MP3 parsing logic and represents a classic example of improper input validation leading to memory corruption issues.
The operational impact of this vulnerability extends beyond simple application instability to potentially enable remote code execution attacks on affected systems. When the cachedBits counter underflows, it creates invalid bit manipulation states that can cause the application to crash or behave unpredictably during audio processing operations. In more severe scenarios, attackers can craft specific MP3 files that exploit this condition to achieve arbitrary code execution within the context of the running application, effectively compromising the entire system. The vulnerability affects any application utilizing the ESP32-audioI2S library for MP3 playback, making it particularly dangerous in embedded environments where such libraries are commonly deployed.
This vulnerability aligns with CWE-191, which specifically addresses integer underflow conditions that occur when a signed integer is decremented below its minimum value. The flaw also corresponds to ATT&CK technique T1203, which involves the exploitation of input validation weaknesses to gain unauthorized system access or execute malicious code. The attack surface is particularly concerning given the widespread use of ESP32 microcontrollers in IoT devices, audio applications, and embedded systems where this library is commonly integrated. Organizations deploying these systems must recognize that the vulnerability could enable attackers to compromise device integrity and potentially use compromised devices as entry points for broader network infiltration.
Mitigation strategies should focus on immediate code modifications to validate the nBits parameter before processing bit operations, ensuring proper bounds checking and preventing negative counter values from occurring. The recommended fix involves implementing input validation routines that verify the nBits parameter falls within acceptable ranges and adding defensive programming measures such as explicit zero-initialization of counters and overflow detection mechanisms. Additionally, users should upgrade to patched versions of the ESP32-audioI2S library once available, while implementing network-level filtering to prevent potentially malicious MP3 files from reaching affected systems. Organizations should also consider implementing runtime monitoring and anomaly detection for audio processing components to identify potential exploitation attempts.