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 55% 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
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 9.8Exploit: Elevated riskExposed: 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)
EG Risk
75(Attend)
EG Risk 75/100SSVC: Attend

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
1%
EPSS %ILE
45%
KEV
Not listed

Published

May 12, 2026

Last Modified

May 18, 2026

Advisory Details (1)

Auto-updated Sep 9, 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 / 29× 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 150 total refreshes for this CVE.

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

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 1% probability of exploitation in the next 30 days, which ranks it in the top 54.6% of all scored CVEs.
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.

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