The vulnerability CVE-2026-25532 affects the Espressif Internet of Things Development Framework (esp-idf), specifically in versions 5.1.6, 5.2.6, 5.3.4, 5.4.3, and 5.5.2. It resides in the Wi-Fi Protected Setup (WPS) Enrollee implementation, where the processing of EAP-Expanded (WSC) messages involves calculating a fragment length (frag_len) by subtracting header sizes from the total packet length. An attacker can send malformed EAP-WSC packets with truncated payloads that omit expected fields such as the 2-byte Message Length when the WPS_MSG_FLAG_LEN flag is set. This causes frag_len to become negative. Since frag_len is then implicitly cast to an unsigned size_t type when passed to the wpabuf_put_data() function, it results in a very large value, leading to buffer overflows or memory corruption. This integer underflow (CWE-191) can cause denial of service by crashing the device or potentially enable further exploitation depending on the memory corruption impact. The vulnerability requires an attacker to send crafted packets over the network to a vulnerable device, and user interaction is limited to the device processing these packets. Espressif has released patches in versions 5.1.7, 5.2.7, 5.3.5, 5.4.4, and 5.5.3 to address this issue. No public exploits have been reported yet, but the medium CVSS score (6.3) reflects the moderate risk due to the network attack vector and potential for availability impact.

For European organizations deploying IoT devices based on esp-idf, this vulnerability could lead to denial of service conditions, causing device outages or instability in critical infrastructure or consumer environments. Given the widespread use of Espressif chips in smart home devices, industrial sensors, and other IoT applications, disruption could affect operational continuity and service availability. While the vulnerability does not directly impact confidentiality or integrity, denial of service in IoT environments can have cascading effects, especially in sectors like manufacturing, energy, and smart city deployments prevalent in Europe. The requirement for network access means that attackers could exploit this remotely if devices are exposed or reachable through internal networks. The absence of known exploits reduces immediate risk, but the medium severity and ease of triggering the flaw through malformed packets necessitate prompt remediation to prevent potential attacks.

European organizations should immediately update esp-idf to the patched versions 5.1.7, 5.2.7, 5.3.5, 5.4.4, or 5.5.3 depending on their current version. For devices already deployed and difficult to update, network segmentation and strict firewall rules should be applied to limit exposure of IoT devices to untrusted networks. Monitoring network traffic for anomalous or malformed EAP-WSC packets can help detect attempted exploitation. Additionally, disabling WPS functionality on devices where it is not required can reduce the attack surface. Vendors and integrators should verify firmware versions and ensure secure update mechanisms are in place. Finally, organizations should conduct security assessments of their IoT deployments to identify vulnerable devices and prioritize patching or mitigation accordingly.