CVE-2026-42855 HIGH

CVE-2026-42855: arduino-esp32: Digest authentication URI mismatch bypass in WebServer allows cross-resource replay attack

Vendor Espressif
Product arduino-esp32
Weakness CWE-287 · Improper authentication
Published May 12, 2026
Last update May 13, 2026

CVSS base score

7.5/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality High
Integrity None

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

What the vulnerability does

01Description

arduino-esp32 is an Arduino core for the ESP32, ESP32-S2, ESP32-S3, ESP32-C3, ESP32-C6 and ESP32-H2 microcontrollers. Prior to 3.3.8, the WebServer Digest authentication implementation in arduino-esp32 computes the authentication hash using the URI field from the client's Authorization header, without verifying that it matches the actual requested URI. This allows an attacker who possesses any valid digest response (computed for URI-A) to authenticate requests to a completely different protected URI (URI-B), bypassing per-resource access control. This vulnerability is fixed in 3.3.8.

Key dates

02Disclosure timeline

May 12, 2026 CVE published
May 13, 2026 Record updated