CVE-2026-20430

High

Published: 02 March 2026

Published

02 March 2026

Modified

02 March 2026

KEV Added

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Patch

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CVSS Score 8.8 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Score 0.0002 6.7th percentile

Risk Priority 18 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-20430 is a high-severity Out-of-bounds Write (CWE-787) vulnerability in Openwrt Openwrt. Its CVSS base score is 8.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 6.7th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-16 (Memory Protection).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 1 other technique. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-10 Information Input Validation good match

prevent

Enforces validation of wireless inputs with proper bounds checking to directly prevent the out-of-bounds write vulnerability in WLAN AP firmware.

SI-16 Memory Protection good match

prevent

Implements memory protection mechanisms such as stack guards and address randomization to block exploitation of the out-of-bounds write for privilege escalation.

SI-2 Flaw Remediation good match

prevent

Requires timely application of the vendor patch WCNCR00467553 to remediate the specific bounds check flaw in MediaTek WLAN AP firmware.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1210 Exploitation of Remote Services Lateral Movement

Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.

attack.mitre.org →

Why these techniques?

Out-of-bounds write in WLAN AP firmware enables unauthenticated remote code execution from adjacent network, directly mapping to public-facing service and remote service exploitation.

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

In wlan AP FW, there is a possible out of bounds write due to an incorrect bounds check. This could lead to remote (proximal/adjacent) escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation.…

Patch ID: WCNCR00467553; Issue ID: MSV-5151.

Deeper analysisAI

CVE-2026-20430 is an out-of-bounds write vulnerability stemming from an incorrect bounds check in WLAN Access Point (AP) firmware developed by MediaTek. This flaw, tracked under CWE-787, affects the firmware component responsible for handling wireless network operations. It was publicly disclosed on March 2, 2026, and carries a CVSS v3.1 base score of 8.8, reflecting its high severity due to the potential for significant impact on confidentiality, integrity, and availability.

Attackers positioned in the adjacent network segment, such as within proximal physical range (e.g., Wi-Fi proximity), can exploit this vulnerability remotely without requiring authentication privileges or user interaction. Successful exploitation enables escalation of privilege on the affected device, potentially allowing arbitrary code execution or system compromise with no additional execution privileges needed.

MediaTek's March 2026 Product Security Bulletin provides details on mitigation, including Patch ID WCNCR00467553 for addressing Issue ID MSV-5151. Security practitioners should apply this patch to vulnerable WLAN AP firmware deployments and monitor for updates via the referenced advisory at https://corp.mediatek.com/product-security-bulletin/March-2026.