ESPAsyncWebServer multipart parser has null-pointer write

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-62966
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-30 21:17:15 UTC
Updated2026-11-06 19:17:54 UTC
DescriptionESPAsyncWebServer is an asynchronous HTTP and WebSocket server library for ESP32, ESP8266, RP2040 and RP2350. Prior to version 3.11.2, the multipart parser in `src/WebRequest.cpp` frees `_itemBuffer` and sets it to NULL when `BOUNDARY_OR_DATA` matches the closing boundary of a file part, before confirming the following terminator, while leaving `_itemIsFile` true. If the next byte is neither the final closing dashes nor a clean CRLF, the `DASH3_OR_RETURN2` or `EXPECT_FEED2` rewind branch re-injects provisionally consumed bytes through `itemWriteByte`. Because `_itemIsFile` remains true, `_itemBuffer`[`_itemBufferIndex`++] writes through a null pointer. On ESP32 this causes a `StoreProhibited` exception, panic and device reboot, producing remote denial of service. A route with a non-trivial body/upload handler, such as a file-upload or web-OTA endpoint, must be present. This issue is fixed in version 3.11.2.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.004260000 probability, percentile 0.371620000 (date 2026-11-08)

Problem Types: CWE-476 | CWE-672 | CWE-476 CWE-476: NULL Pointer Dereference | CWE-672 CWE-672: Operation on a Resource after Expiration or Release

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA ESP32Async ESPAsyncWebServer affected < 3.11.2 Not specified

References

ReferenceSourceLinkTags
github.com/ESP32Async/ESPAsyncWebServer/tree/v3.11.2 [email protected] github.com
github.com/ESP32Async/ESPAsyncWebServer/commit/4efbd35e597d91f01749f2d4a... [email protected] github.com
github.com/ESP32Async/ESPAsyncWebServer/security/advisories/GHSA-8m8p-vh... [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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