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CVE-2026-42855

Espressif Arduino-esp32 authentication bypass

7.5 HIGHPublic exploitEPSS 0.51%
  1. Published12 May 2026

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityNone
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected products

Espressif Arduino-esp32< 3.3.8

Remediation

Fixed in
Espressif Arduino-esp32≥ 3.3.8

References

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Frequently asked

Is CVE-2026-42855 being actively exploited?

CVE-2026-42855 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.51%.

How severe is CVE-2026-42855?

CVE-2026-42855 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.51% probability of exploitation.

Which products are affected by CVE-2026-42855?

Affected products include Espressif Arduino-esp32.

How do I fix CVE-2026-42855?

Upgrade affected software to a fixed version, for example Espressif Arduino-esp32 3.3.8 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-42855 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.