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VulnerabilityPublished

CVE-2026-42854: espressif arduino-esp32 · Stack-based Buffer Overflow

Affects espressif arduino-esp32Source CVE Database V5

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Not known to be exploited · CVSS 9.8 Critical : upgrade to 3.3.8 as a priority.

Data as of 11 Nov 2026, 23:24 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.

Contested

Critical score, yet low EPSS after six months
EPSS
0.5% chance of exploitation in 30 days – higher than 47% 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:H/A:H

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 11 Nov 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 patch is available in arduino-esp32 version 3.3.8 that fixes this vulnerability. Users should upgrade to version 3.3.8 or later to remediate the issue. Since this is a cloud service environment, the vendor manages remediation for the cloud-hosted service; users should verify with the vendor that updates have been applied. No additional mitigation steps are indicated in the advisory.

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 multipart form parser in arduino-esp32 allocates a Variable Length Array (VLA) on the stack whose size is derived from an attacker-controlled HTTP header field (Content-Type: multipart/form-data; boundary=...) without enforcing any length limit. Sending a boundary string longer than ~8000 characters overflows the 8192-byte task stack of the loopTask, causing a crash and potential remote code execution. This vulnerability is fixed in 3.3.8.

References

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