What’s Vulnerable › Vulnerabilities
CVE-2026-42855: arduino-esp32: Digest authentication URI mismatch bypass in WebServer allows cross-resource replay attack
- Severity: high (CVSS 7.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.4% probability of exploitation in the next 30 days
- Public exploit or detection template: yes
- Published: 2026-05-12 · updated 2026-10-26
- Weakness: CWE-287
Description
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 products
- espressif arduino-esp32: before 3.3.8 — fixed in 3.3.8
How to fix
Upgrade to a fixed version: espressif arduino-esp32 3.3.8. Check the vendor advisory for mitigations.
References
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