CVE-2026-62966

HIGH CVSS 7.5 PoC Available

Published: 2026-10-30

Modified: 2026-10-30

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AI Threat Summary

CVE-2026-62966 is a high-severity vulnerability with a CVSS score of 7.5 affecting the target software. Threat hunters should monitor for exploit attempts and apply vendor patches immediately.

Description

ESPAsyncWebServer 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.

Attack Chain

Reconnaissance

Attacker scans for vulnerable versions using version banners or PoC scanners

Initial Access

Attacker triggers CVE-2026-62966 vulnerability with a crafted request or payload

Execution

Vulnerability exploited to perform unauthorized actions on the target system

Impact

Depending on vulnerability type, attacker achieves data access, service disruption, or code execution

MITRE ATT&CK Techniques

T1190 Exploit Public-Facing Application

Initial Access

Public-facing application vulnerability exploited for initial access

T1203 Exploitation for Client Execution

Execution

Vulnerability exploited to execute attacker-controlled code

Indicators of Compromise

Type	Value	Description
user_agent	`Mozilla/5.0 (compatible; exploit/1.0)`	Generic exploit scanner user agent pattern
url	`/api/vuln-endpoint?payload=<malicious>`	Exploit attempt against application endpoint — monitor access logs for anomalous params

Remediation

1. Apply vendor-supplied security patches immediately. 2. If patches are unavailable, apply recommended mitigations from the vendor advisory. 3. Enable WAF rules or IDS signatures to detect exploitation attempts. 4. Monitor logs for indicators of compromise listed above. 5. Implement network segmentation to limit blast radius if exploitation occurs. 6. Subscribe to vendor security advisories for this product.

Quick Facts

CVE ID	CVE-2026-62966
CVSS Score	7.5
Vector	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`
Published	2026-10-30
Exploited	No
CISA KEV	No
PoC	Available

References

External Resources

NVD Entry BleepingComputer The Hacker News