Auth bypass in Espressif Arduino-Esp32
CVE-2026-42855
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.
Vulnerability class: Broken Authentication
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.005 (40.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 41st percentile — 40.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.002
Affected products
- Espressif Arduino-Esp32 — versions < 3.3.8
Weakness classification (CWE)
References
- github.com/espressif/arduino-esp32/security/advisories/GHSA-28hv-fwm3-rpcq (Exploit, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-42855?
- CVE-2026-42855 is a high-severity vulnerability in Espressif Arduino-Esp32, classified under Improper Authentication. CVSS score: 7.5/10. Published 2026-05-12.
- How severe is CVE-2026-42855?
- High severity. CVSS v3 base score is 7.5 out of 10.