CVE-2026-87121
Received Received - Intake

Out-of-Bounds Write in lwIP TCP/IP Stack MQTT

Publication date: 2026-09-22

Last updated on: 2026-09-22

Assigner: ICS-CERT

Description
lwIP TCP/IP Stack MQTT is vulnerable to an out-of-bounds write, which may allow an attacker to gain full code execution on the device.

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Meta Information

Published
2026-09-22
Last Modified
2026-09-22
Generated
2026-09-23
AI Q&A
2026-09-22
EPSS Evaluated
N/A
NVD
CVE-2026-87121
EUVD
EUVD-2026-84816

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
lwip lwip 2.2.1
lwip tcp_ip_stack *

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-787 The product writes data past the end, or before the beginning, of the intended buffer.

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Executive Summary

This vulnerability is an out-of-bounds write in the lwIP TCP/IP Stack's MQTT implementation. It allows an attacker to execute arbitrary code on the affected device by exploiting improper memory handling during MQTT protocol operations.

Impact Analysis

An attacker could gain full control over the device, leading to potential data theft, device manipulation, or disruption of services. This is especially critical for networked devices relying on lwIP for MQTT communication.

Compliance Impact

This vulnerability could lead to unauthorized access or data breaches, violating confidentiality requirements in GDPR and HIPAA. Organizations may face legal penalties and reputational damage if exploited.

Mitigation Strategies

Update lwIP TCP/IP stack to the latest patched version immediately. Disable MQTT protocol if not required. Monitor network traffic for unusual MQTT activity. Apply network segmentation to limit exposure.

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