CVE-2026-25508 in ESP-IDF
Summary
by MITRE • 02/04/2026
ESF-IDF is the Espressif Internet of Things (IOT) Development Framework. In versions 5.5.2, 5.4.3, 5.3.4, 5.2.6, and 5.1.6, an out-of-bounds read vulnerability was reported in the BLE ATT Prepare Write handling of the BLE provisioning transport (protocomm_ble). The issue can be triggered by a remote BLE client while the device is in provisioning mode. The transport accumulated prepared-write fragments in a fixed-size buffer but incorrectly tracked the cumulative length. By sending repeated prepare write requests with overlapping offsets, a remote client could cause the reported length to exceed the allocated buffer size. This inflated length was then passed to provisioning handlers during execute-write processing, resulting in an out-of-bounds read and potential memory corruption. This issue has been patched in versions 5.5.3, 5.4.4, 5.3.5, 5.2.7, and 5.1.7.
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Analysis
by VulDB Data Team • 02/20/2026
The vulnerability CVE-2026-25508 represents a critical out-of-bounds read condition within the Espressif Internet of Things Development Framework, specifically affecting BLE provisioning transport functionality. This issue resides in the protocomm_ble component responsible for handling Bluetooth Low Energy ATT Prepare Write operations during device provisioning. The vulnerability stems from improper buffer management where the system accumulates prepared-write fragments in a fixed-size buffer while maintaining an incorrect cumulative length counter. This flaw allows remote attackers to manipulate the buffer tracking mechanism through carefully crafted prepare write requests with overlapping memory offsets.
The technical implementation of this vulnerability demonstrates a classic buffer overflow scenario where memory boundaries are exceeded due to flawed length calculation. During BLE provisioning mode, when a remote client sends multiple prepare write requests with overlapping offset values, the system incorrectly updates its internal length tracking variable. This inflated length value eventually gets passed to provisioning handlers during execute-write processing, causing the system to read beyond the allocated buffer boundaries. The flaw is particularly dangerous because it occurs during the provisioning phase when devices are typically more exposed to network access and remote interaction.
The operational impact of this vulnerability extends beyond simple memory corruption to potentially enable remote code execution or information disclosure attacks. Attackers can exploit this condition to access memory locations outside the intended buffer boundaries, potentially reading sensitive data from adjacent memory regions or corrupting system memory structures. The vulnerability affects multiple major versions of the Espressif framework, indicating a widespread exposure across various IoT deployments that rely on BLE provisioning for device configuration and management. This creates significant risk for IoT ecosystems where devices may be remotely provisioned and where security boundaries are not properly enforced.
Security implications of this vulnerability align with CWE-125 Out-of-bounds Read and CWE-787 Out-of-bounds Write patterns, representing a fundamental memory safety issue in embedded systems. The ATT&CK framework categorizes this as a remote code execution vector through protocol manipulation, specifically targeting the network services component. Organizations deploying Espressif-based IoT solutions must consider the potential for persistent compromise, as successful exploitation could allow attackers to gain control over device provisioning processes and potentially establish footholds within larger IoT networks. The vulnerability highlights the importance of proper buffer boundary checking in embedded systems where memory constraints and resource limitations make such flaws particularly dangerous.
Mitigation strategies should prioritize immediate firmware updates to patched versions 5.5.3, 5.4.4, 5.3.5, 5.2.7, and 5.1.7, which address the buffer tracking logic and implement proper bounds checking. Network segmentation and access controls should be implemented to limit BLE provisioning access to trusted networks and authorized clients. Additional defensive measures include monitoring for anomalous prepare write request patterns and implementing rate limiting for provisioning operations. System administrators should conduct thorough vulnerability assessments of all IoT devices using affected framework versions and consider implementing intrusion detection systems to monitor for exploitation attempts. The fix addresses the root cause by correcting the cumulative length calculation and ensuring proper buffer boundary validation during BLE provisioning operations.