CVE-2026-25532 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, a vulnerability exists in the WPS (Wi-Fi Protected Setup) Enrollee implementation where malformed EAP-WSC packets with truncated payloads can cause integer underflow during fragment length calculation. When processing EAP-Expanded (WSC) messages, the code computes frag_len by subtracting header sizes from the total packet length. If an attacker sends a packet where the EAP Length field covers only the header and flags but omits the expected payload (such as the 2-byte Message Length field when WPS_MSG_FLAG_LEN is set), frag_len becomes negative. This negative value is then implicitly cast to size_t when passed to wpabuf_put_data(), resulting in a very large unsigned value. 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 identified as CVE-2026-25532 resides within the Espressif Internet of Things Development Framework, specifically affecting versions 5.5.2, 5.4.3, 5.3.4, 5.2.6, and 5.1.6. This issue manifests in the WPS (Wi-Fi Protected Setup) Enrollee implementation where the framework processes EAP-WSC (Extensible Authentication Protocol with Wi-Fi Simple Configuration) packets. The flaw occurs during the handling of EAP-Expanded messages, which are fundamental to the WPS authentication process used in IoT device provisioning. The vulnerability represents a critical security weakness that could potentially compromise the integrity and availability of Wi-Fi protected networks.
The technical root cause of this vulnerability lies in the improper handling of packet length calculations during EAP-WSC message processing. When the framework receives an EAP-Expanded packet, it calculates the fragment length by subtracting header sizes from the total packet length. However, when an attacker crafts a malformed packet with truncated payloads, specifically one where the EAP Length field only encompasses the header and flags without the expected payload data, the calculation results in a negative value. This occurs because the packet structure violates the expected WPS message format where certain fields like the 2-byte Message Length field are mandatory when WPS_MSG_FLAG_LEN is set. The negative integer value then undergoes implicit casting to size_t type, which transforms the negative value into an extremely large unsigned integer.
This transformation creates a severe memory management issue that can lead to buffer overflows and arbitrary code execution. The large unsigned value passed to wpabuf_put_data() function causes the system to attempt to allocate or manipulate memory regions far beyond the actual packet boundaries, potentially corrupting adjacent memory structures or causing the application to crash. The vulnerability aligns with CWE-191, which describes integer underflow conditions, and represents a classic example of improper input validation that can be exploited through crafted network traffic. The attack vector is particularly dangerous as it requires only network access to send malformed packets, making it suitable for remote exploitation in wireless environments.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to potentially enable more sophisticated attacks against IoT devices running affected versions of the Espressif framework. Devices that rely on WPS for network provisioning become vulnerable to attackers who can craft malicious EAP-WSC packets to trigger the integer underflow condition. This could result in device crashes, memory corruption, or potentially allow attackers to execute arbitrary code on the affected devices. The vulnerability affects a wide range of IoT deployments where WPS functionality is enabled, including smart home devices, industrial sensors, and enterprise IoT infrastructure. Given that many IoT devices may not receive regular security updates, this vulnerability could remain unpatched for extended periods, creating persistent security risks in connected environments. Organizations using these frameworks should immediately implement mitigations to prevent exploitation.
The security community should note that this vulnerability demonstrates the importance of robust input validation and proper integer handling in network protocol implementations. The issue highlights how seemingly minor flaws in packet parsing logic can lead to severe security consequences, particularly in embedded systems where memory constraints and resource limitations make such vulnerabilities more dangerous. The patching process for this vulnerability requires updating to versions 5.5.3, 5.4.4, 5.3.5, 5.2.7, and 5.1.7, which contain the necessary fixes to prevent the integer underflow condition. Organizations should conduct thorough testing of updated firmware to ensure compatibility and verify that the fix properly addresses the underlying memory management issue. The vulnerability also underscores the need for continuous security assessment of IoT frameworks, as the interconnected nature of these systems means that a single flaw can impact entire ecosystems of connected devices.