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VulnerabilityPublished

CVE-2026-42855: espressif arduino-esp32 · Improper Authentication

Affects espressif arduino-esp32Source CVE Database V5

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Not known to be exploited · CVSS 7.5 High : upgrade to 3.3.8 soon.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 28% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 3.3.8
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 12 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade arduino-esp32 and espressif/arduino-esp32 to 3.3.8.

Affected software

ProductAffectedFixed in
espressifarduino-esp32Affected
  • <3.3.8
Fixed in
  • 3.3.8
GitHubespressif/arduino-esp32pkg:github/espressif/arduino-esp32Other threatsAffected
  • <3.3.8
Fixed in
  • 3.3.8

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in arduino-esp32 version 3.3.8. Users should upgrade to version 3.3.8 or later to remediate this vulnerability. Since this is a cloud service managed by the vendor, the vendor is responsible for patching the hosted service. Check the vendor advisory for confirmation of patch deployment status.

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.

References

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