CVE-2026-51261 in ESP32-audioI2S
Summary
by MITRE • 07/28/2026
Missing mutex synchronization in AudioBuffer::freeSpace() in schreibfaul1 ESP32-audioI2S 3.4.5 creates a race condition between concurrent tasks. The function calculates available buffer space without protecting shared read/write pointers, returning an incorrectly large value. Trusting this value leads to heap out-of-bounds write, memory corruption, device crash, and arbitrary code execution.
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Analysis
by VulDB Data Team • 07/28/2026
The vulnerability exists within the schreibfaul1 ESP32-audioI2S library version 3.4.5 where the AudioBuffer::freeSpace() function lacks proper mutex synchronization mechanisms. This critical flaw manifests as a race condition that can be exploited by concurrent tasks attempting to access the audio buffer simultaneously. The absence of protective synchronization primitives allows multiple threads or tasks to read and modify shared buffer pointers concurrently, leading to unpredictable behavior and data corruption.
The technical implementation flaw stems from the function's failure to protect the shared read/write pointers that track buffer usage and available space. When multiple tasks execute concurrently, they may access these pointers without proper mutual exclusion, causing the freeSpace() calculation to return an incorrect value that represents more available space than actually exists. This miscalculation occurs because the function does not serialize access to the critical sections that manage buffer state information.
The operational impact of this vulnerability extends beyond simple memory corruption to encompass complete system instability and potential remote code execution capabilities. When applications trust the incorrectly calculated buffer space values, they may attempt to write data beyond the actual heap boundaries, resulting in out-of-bounds memory writes that corrupt adjacent memory regions. This memory corruption can trigger device crashes, system panics, or more insidiously lead to arbitrary code execution scenarios where malicious actors could gain control over the device's execution flow.
The vulnerability aligns with CWE-362, which specifically addresses race conditions in concurrent programming, and represents a classic example of improper synchronization in shared resource access. From an attack perspective, this weakness maps to several ATT&CK techniques including T1059 for code execution and T1499 for system disruption. The exploitation requires only concurrent task execution patterns that are common in audio processing applications, making it particularly dangerous in embedded systems where such concurrency is expected.
Mitigation strategies must focus on implementing proper mutex synchronization around the buffer pointer access within the freeSpace() function. The recommended approach involves wrapping all critical sections that modify or read the shared read/write pointers with appropriate locking mechanisms to ensure atomic access. Additionally, input validation should be implemented to verify calculated buffer space values against actual memory boundaries before any write operations occur. Regular updates to the library should include comprehensive testing of concurrent scenarios and formal verification of synchronization primitives to prevent similar issues in future releases.