CVE-2026-42854: espressif arduino-esp32 · Stack-based Buffer Overflow
Affects espressif arduino-esp32Source CVE Database V5
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
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:HExploitation evidence
Disclosed: evidence found.
CVE published 12 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
| espressifarduino-esp32 | Affected
| Fixed in
|
GitHubespressif/arduino-esp32pkg:github/espressif/arduino-esp32Other threats | Affected
| Fixed in
|
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.