CVE-2026-42854

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 0.6%, top 57% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Elevated
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 9.8Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
9.8
EG Score
9.8(medium)
EPSS
43.4%
KEV
Not listed

Published

May 12, 2026

Last Modified

May 18, 2026

Advisory Details (1)

Auto-updated Jun 21, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

Stack buffer overflow in WebServer multipart boundary parsing leads to remote crash potential RCE · Advisory · espressif/arduino-esp32 · GitHub

https://github.com/espressif/arduino-esp32/security/advisories/GHSA-8cmm-3887-r32j

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 7× in last 7d / 50× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 176 total refreshes for this CVE.

  1. 2026-07-15 16:57 UTCEPSS rescore
  2. 2026-07-15 02:00 UTCEPSS rescore
  3. 2026-07-13 22:30 UTCEPSS rescore
  4. 2026-07-13 06:13 UTCEPSS rescore
  5. 2026-07-12 05:46 UTCEPSS rescore
  6. 2026-07-11 08:27 UTCEPSS rescore
  7. 2026-07-09 19:10 UTCEPSS rescore
  8. 2026-07-08 15:16 UTCEPSS rescore
  9. 2026-07-07 13:46 UTCEPSS rescore
  10. 2026-07-06 16:27 UTCEPSS rescore
  11. 2026-07-06 16:27 UTCEPSS rescore
  12. 2026-07-06 02:23 UTCEPSS rescore
  13. 2026-07-06 02:23 UTCEPSS rescore
  14. 2026-07-05 02:30 UTCEPSS rescore
  15. 2026-07-04 06:31 UTCEPSS rescore
  16. 2026-07-01 15:06 UTCEPSS rescore
  17. 2026-06-30 23:22 UTCEPSS rescore
  18. 2026-06-29 14:06 UTCEPSS rescore
  19. 2026-06-28 14:07 UTCEPSS rescore
  20. 2026-06-28 12:56 UTCEG score recompute
  21. 2026-06-28 08:22 UTCEG score recompute
  22. 2026-06-28 04:56 UTCEPSS rescore
  23. 2026-06-28 04:07 UTCEG score recompute
  24. 2026-06-27 23:58 UTCEG score recompute
  25. 2026-06-27 13:14 UTCEG score recompute
Show 75 more
  1. 2026-06-27 08:17 UTCEG score recompute
  2. 2026-06-27 03:08 UTCEPSS rescore
  3. 2026-06-26 20:41 UTCEG score recompute
  4. 2026-06-26 04:00 UTCEG score recompute
  5. 2026-06-25 20:30 UTCEG score recompute
  6. 2026-06-25 13:49 UTCEPSS rescore
  7. 2026-06-25 13:49 UTCEPSS rescore
  8. 2026-06-24 14:05 UTCEPSS rescore
  9. 2026-06-23 21:33 UTCEPSS rescore
  10. 2026-06-22 14:25 UTCEPSS rescore
  11. 2026-06-22 14:25 UTCEPSS rescore
  12. 2026-06-21 14:56 UTCEPSS rescore
  13. 2026-06-21 14:56 UTCEPSS rescore
  14. 2026-06-21 01:59 UTCEPSS rescore
  15. 2026-06-19 19:25 UTCEPSS rescore
  16. 2026-06-18 17:52 UTCEPSS rescore
  17. 2026-06-18 17:52 UTCEPSS rescore
  18. 2026-06-17 21:46 UTCEG score recompute
  19. 2026-06-17 17:53 UTCEPSS rescore
  20. 2026-06-17 14:56 UTCEG score recompute
  21. 2026-06-17 03:17 UTCEG score recompute
  22. 2026-06-16 23:07 UTCEG score recompute
  23. 2026-06-16 17:52 UTCEPSS rescore
  24. 2026-06-16 08:01 UTCEG score recompute
  25. 2026-06-16 03:53 UTCEG score recompute
  26. 2026-06-15 17:49 UTCEPSS rescore
  27. 2026-06-15 07:58 UTCEG score recompute
  28. 2026-06-15 03:07 UTCEG score recompute
  29. 2026-06-14 22:57 UTCEG score recompute
  30. 2026-06-14 18:49 UTCEG score recompute
  31. 2026-06-14 14:41 UTCEG score recompute
  32. 2026-06-14 10:34 UTCEG score recompute
  33. 2026-06-14 06:24 UTCEG score recompute
  34. 2026-06-13 23:59 UTCEG score recompute
  35. 2026-06-13 23:00 UTCEPSS rescore
  36. 2026-06-13 06:45 UTCEG score recompute
  37. 2026-06-13 02:01 UTCEG score recompute
  38. 2026-06-12 23:12 UTCEPSS rescore
  39. 2026-06-12 23:12 UTCEPSS rescore
  40. 2026-06-12 21:53 UTCEG score recompute
  41. 2026-06-12 17:45 UTCEG score recompute
  42. 2026-06-12 13:37 UTCEG score recompute
  43. 2026-06-12 09:25 UTCEG score recompute
  44. 2026-06-12 05:17 UTCEG score recompute
  45. 2026-06-12 01:09 UTCEG score recompute
  46. 2026-06-11 21:02 UTCEG score recompute
  47. 2026-06-11 16:54 UTCEG score recompute
  48. 2026-06-11 14:00 UTCEPSS rescore
  49. 2026-06-11 11:21 UTCEG score recompute
  50. 2026-06-11 07:12 UTCEG score recompute
  51. 2026-06-11 03:04 UTCEG score recompute
  52. 2026-06-10 22:56 UTCEG score recompute
  53. 2026-06-10 22:18 UTCEPSS rescore
  54. 2026-06-10 18:48 UTCEG score recompute
  55. 2026-06-10 14:41 UTCEG score recompute
  56. 2026-06-10 13:22 UTCEPSS rescore
  57. 2026-06-10 13:22 UTCEPSS rescore
  58. 2026-06-10 10:33 UTCEG score recompute
  59. 2026-06-10 06:25 UTCEG score recompute
  60. 2026-06-10 02:18 UTCEG score recompute
  61. 2026-06-09 22:10 UTCEG score recompute
  62. 2026-06-09 16:45 UTCEG score recompute
  63. 2026-06-09 12:37 UTCEG score recompute
  64. 2026-06-09 08:30 UTCEG score recompute
  65. 2026-06-09 04:22 UTCEG score recompute
  66. 2026-06-09 00:14 UTCEG score recompute
  67. 2026-06-08 20:06 UTCEG score recompute
  68. 2026-06-08 14:17 UTCEPSS rescore
  69. 2026-06-08 14:17 UTCEPSS rescore
  70. 2026-06-08 11:50 UTCEG score recompute
  71. 2026-06-08 07:42 UTCEG score recompute
  72. 2026-06-08 03:34 UTCEG score recompute
  73. 2026-06-07 23:27 UTCEG score recompute
  74. 2026-06-07 19:20 UTCEG score recompute
  75. 2026-06-07 15:25 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-42854?
CVE-2026-42854 is a critical vulnerability published on May 12, 2026. 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…
When was CVE-2026-42854 disclosed?
CVE-2026-42854 was first published in the National Vulnerability Database on May 12, 2026, with the most recent update on May 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-42854 actively exploited?
CVE-2026-42854 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 43.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-42854?
CVE-2026-42854 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2026-42854?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-42854, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-42854

Explore →

Is Your Infrastructure Affected by CVE-2026-42854?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs