CVE-2026-42855: arduino-esp32: Digest authentication URI mismatch bypass in WebServer allows cross-resource replay attack
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.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-42855?
CVE-2026-42855 has been identified as a moderate severity vulnerability due to its potential for cross-resource replay attacks.
How do I fix CVE-2026-42855?
To mitigate CVE-2026-42855, upgrade the Arduino-ESP32 library to version 3.3.8 or later.
What does CVE-2026-42855 exploit?
CVE-2026-42855 exploits a Digest authentication URI mismatch in the WebServer of the Arduino-ESP32, leading to authentication bypass.
Who is affected by CVE-2026-42855?
CVE-2026-42855 affects users of the Arduino-ESP32 core for versions prior to 3.3.8.
What type of attack is associated with CVE-2026-42855?
CVE-2026-42855 allows for a cross-resource replay attack due to its authentication vulnerability.