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CVE-2026-87121— Out-of-bounds write in lwIP TCP/IP Stack MQTT Client Application

Quick assessment

Affected
lwIP TCP/IP Stack MQTT
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

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.

CVSS 9.8 · Critical
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I. Basic Information for CVE-2026-87121

Vulnerability Information

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Vulnerability Title
Out-of-bounds write in lwIP TCP/IP Stack MQTT Client Application
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存写
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
lwIP TCP/IP Stack MQTT 2.0.1 ~ 2.2.1 -

II. Public POCs for CVE-2026-87121

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III. Intelligence Information for CVE-2026-87121

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Other References for CVE-2026-87121 (3)

IV. Related Vulnerabilities

Same vendor: lwIP
Same weakness: CWE-787

V. Comments for CVE-2026-87121

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