CVE Catalog

CVE-2026-54571

HighCVSS 8.7
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.52%

42th percentile - higher than 42% of all known CVEs

Summary

In ESPAsyncWebServer (an asynchronous HTTP and WebSocket server library for ESP32, ESP8266, RP2040 and RP2350) before version 3.11.1, the multipart/form-data parser in src/WebRequest.cpp stores _boundaryPosition as an 8-bit value while _parseMultipartPostByte processes the boundary. A remote request containing an exactly 256-byte multipart boundary wraps _boundaryPosition from 255 to zero, prevents the boundary parsing loop from terminating, consumes excessive CPU, and triggers a FreeRTOS watchdog reset on affected ESP32 or ESP8266 devices. The issue is fixed in version 3.11.1.

Risk Assessment

A remote attacker can cause the parsing loop to hang, consume excessive CPU, and trigger a watchdog reset with a single request, restarting the device and disrupting service. This affects ESP32 and ESP8266 devices.

Recommendation

Update the ESPAsyncWebServer library to version 3.11.1 or later. Until then, consider restricting access to devices and monitoring for unexpected reboots.

Related vulnerabilities

Original NVD description (English source)

ESPAsyncWebServer is an asynchronous HTTP and WebSocket server library for ESP32, ESP8266, RP2040 and RP2350. Prior to 3.11.1, the multipart/form-data parser in src/WebRequest.cpp stores _boundaryPosition as an 8-bit value while _parseMultipartPostByte processes the boundary. A remote request containing an exactly 256-byte multipart boundary wraps _boundaryPosition from 255 to zero, prevents the boundary parsing loop from terminating, consumes excessive CPU, and triggers a FreeRTOS watchdog reset on affected ESP32 or ESP8266 devices. This issue is fixed in version 3.11.1.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS