EN

CVE-2026-42855

High
7.5
0.05.010.0
Year
2026
Published
May 12, 2026
Known Affected Devices
0
CVSS Score
7.5

What is 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.

CVSS Vector Breakdown

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

Exploitable remotely over the network without requiring access to the local system.

AC
Attack Complexity
Low

No special conditions required. Exploit can be performed reliably and repeatedly.

PR
Privileges Required
None

No authentication required. Any anonymous user can exploit this vulnerability.

UI
User Interaction
None

No user interaction required. Exploit runs without any victim action.

S
Scope
Unchanged

Exploiting the vulnerability only affects the vulnerable component itself.

C
Confidentiality Impact
High

Complete loss of confidentiality. All data on the component may be exposed.

I
Integrity Impact
None

No integrity impact. Data cannot be modified.

A
Availability Impact
None

No availability impact. Service remains fully operational.

FAQ

How severe is CVE-2026-42855?

CVE-2026-42855 has a CVSS score of 7.5/10, rated as High. This is a high severity vulnerability and should be patched as soon as possible.

What does the CVSS score mean for CVE-2026-42855?

CVSS (Common Vulnerability Scoring System) rates vulnerability severity from 0.0 to 10.0. CVE-2026-42855 scores 7.5/10 (High). Scores 9.0–10.0 are Critical, 7.0–8.9 are High, 4.0–6.9 are Medium, and below 4.0 are Low.

Which devices are affected by CVE-2026-42855?

The list of devices confirmed to be affected by CVE-2026-42855 is shown in the "Affected Devices" section above. Check your firmware version against the vendor security advisory and apply the latest patch.

How do I fix or mitigate CVE-2026-42855?

Apply the latest firmware or software update from the vendor. Check the References section above for official advisories and patch notes. If no patch is available, consider disabling the affected feature or isolating the device from untrusted networks.