CVE-2026-87121

Out-of-bounds write in lwIP TCP/IP Stack MQTT Client Application

Published Sep 22, 2026 CVSS 4.0 · 9.3 Critical EPSS < 1% KEV · Not listed
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.

Remediation

Vendor Solution

Users of lwIP are encouraged to update their version of lwIP using the repository found at  https://savannah.nongnu.org/projects/lwip . The commit identifier that contains the fix is f89407ea711879c04d91c92b35d67be78bbaf0f1.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Lwip
Lwip tcp/ip Stack Mqtt
Vendors & Products Lwip
Lwip tcp/ip Stack Mqtt
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title Out-of-bounds write in lwIP TCP/IP Stack MQTT Client Application
Weaknesses CWE-787
References
Metrics cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

cvssV4_0

{'score': 9.3, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
icscert
Published
Updated
Sep 22, 2026, 8:23 PM
Reserved
Sep 9, 2026, 9:28 PM
Status
Awaiting Analysis
Published
Sep 22, 2026, 8:17 PM
Modified
Sep 23, 2026, 7:42 PM