Advisories › lwIP › ICSA-26-265-01
lwIP TCP/IP Stack MQTT Client Application: 1 CVE, Critical 9.8
Summary
CISA reports 1 vulnerability in lwIP MQTT Client Application. Weakness type: Out-of-bounds Write. Successful exploitation of this vulnerability could allow an attacker to gain full code execution on the device. Highest CVSS v3 score: 9.8 (Critical), exploitable over the network.
What to do: Act now: 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.
At a glance
- Vendor
- lwIP
- Products
- MQTT Client Application
- CVEs
- CVE-2026-87121
- Highest CVSS v3
- 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Highest CVSS v4
- –
- Known exploited (KEV)
- No CVE from this advisory is on the KEV list as of the last refresh
- Sectors (per CISA)
- Chemical, Communications, Critical Manufacturing, Energy, Financial Services, Healthcare and Public Health, Transportation Systems, Water and Wastewater Systems
- Deployed
- Worldwide
- Vendor HQ
- Sweden
Vulnerabilities
| CVE | Weakness | CVSS v3 | CVSS v4 | KEV | Description (from advisory) |
|---|---|---|---|---|---|
| CVE-2026-87121 | Out-of-bounds Write | 9.8 | – | No | The affected product is vulnerable to an out-of-bounds write, which may allow an attacker to gain full code execution on the device. |
Affected products (1)
- lwIP MQTT Client Application: >=2.0.1|<=2.2.1
Vendor fixes and mitigations (from advisory)
- Mitigation: 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. link
Also apply CISA's standard ICS practices: minimize network exposure, keep control networks behind firewalls and isolated from business networks, and use up-to-date secure remote access.
Sources
This page is generated automatically from the CISA advisory text. It is not a substitute for the vendor's guidance; verify affected versions and fixes at the source before making changes to control systems.