CVE-2026-54571

HIGHPre-NVD 8.78.7—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.7 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 77% 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, secondary
Trending — 3 sources updated this week
8.7EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.7Exploit: None knownExposed: 0

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

ESPAsyncWebServer is an asynchronous HTTP and WebSocket server library for ESP32, ESP8266, RP2040 and RP2350. Prior to 3.11.1, the multipart/form-data parser in src/WebRequest.cpp stores _boundaryPosition as an 8-bit value while _parseMultipartPostByte processes the boundary. A remote request containing an exactly 256-byte multipart boundary wraps _boundaryPosition from 255 to zero, prevents the boundary parsing loop from terminating, consumes excessive CPU, and triggers a FreeRTOS watchdog reset on affected ESP32 or ESP8266 devices. This issue is fixed in version 3.11.1.

CVSS v3
8.7
EG Score
8.7(medium)
EG Risk
44(Track)
EG Risk 44/100SSVC: Track

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
Severity87% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
23%
KEV
Not listed

Published

September 17, 2026

Last Modified

September 17, 2026

Advisory Details (4)

Auto-updated Sep 17, 2026
Patch available. Sources: github_commit, github_release, github, github_pr.
github_release Patch Available

v3.11.1

Patch available: ESP32Async/ESPAsyncWebServer v3.11.1

https://github.com/ESP32Async/ESPAsyncWebServer/releases/tag/v3.11.1
github_commit Patch Available

commit b928de7cbd7d (ESP32Async/ESPAsyncWebServer)

Patch available: ESP32Async/ESPAsyncWebServer v3.11.1 (contains commit b928de7cbd7d)

https://github.com/ESP32Async/ESPAsyncWebServer/commit/b928de7cbd7debcd6266ece6a6c46f10a86d3a6f
github_pr Patch Available

Fix CWE-190 - DoS could happen with a specially crafted boundary parameter in a multipart request

Patch available: ESP32Async/ESPAsyncWebServer v3.11.1 (PR #445 merged 2026-06-08)

https://github.com/ESP32Async/ESPAsyncWebServer/pull/445
github Patch Available

Integer overflow in multipart boundary parser causes denial of service · Advisory · ESP32Async/ESPAsyncWebServer · GitHub

https://github.com/ESP32Async/ESPAsyncWebServer/security/advisories/GHSA-4phx-fcj6-46r4

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 8× 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.

  1. 2026-09-20 21:39 UTCEG score recompute
  2. 2026-09-20 20:16 UTCEPSS rescore
  3. 2026-09-19 20:54 UTCEG score recompute
  4. 2026-09-18 20:11 UTCEG score recompute
  5. 2026-09-18 19:28 UTCEPSS rescore
  6. 2026-09-17 19:26 UTCEG score recompute
  7. 2026-09-17 18:43 UTCEG score recompute
  8. 2026-09-17 18:39 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-54571?
CVE-2026-54571 is a high vulnerability published on September 17, 2026. ESPAsyncWebServer is an asynchronous HTTP and WebSocket server library for ESP32, ESP8266, RP2040 and RP2350. Prior to 3.11.1, the multipart/form-data parser in src/WebRequest.cpp stores boundaryPosition as an 8-bit value while parseMultipartPostByte processes the boundary. A remote request…
When was CVE-2026-54571 disclosed?
CVE-2026-54571 was first published in the National Vulnerability Database on September 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-54571 actively exploited?
CVE-2026-54571 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 77.0% of all scored CVEs.
What is the CVSS score of CVE-2026-54571?
CVE-2026-54571 has a CVSS v3 base score of 8.7 (NVD).
How do I remediate CVE-2026-54571?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-54571, 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

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