CVE-2026-20543: Modem Logic Error Information Disclosure

CVE-2026-20543 Overview

CVE-2026-20543 is an information disclosure vulnerability in the MediaTek Modem component caused by a logic error. A local attacker with low privileges can obtain sensitive information from the device without requiring additional execution privileges or user interaction. The flaw is classified under [CWE-215: Insertion of Sensitive Information Into Debugging Code]. MediaTek tracks the issue as MSV-6761 with patch identifier MOLY01645293, published in the MediaTek Security Bulletin - October 2026.

Critical Impact
Local attackers can disclose sensitive modem data on affected MediaTek-based devices without user interaction, impacting confidentiality on mobile endpoints.

Affected Products

MediaTek Modem firmware (devices covered by the October 2026 security bulletin)
Android devices using affected MediaTek chipsets
OEM handsets pending integration of patch MOLY01645293

Discovery Timeline

2026-10-05 - CVE-2026-20543 published to NVD
2026-10-06 - Last updated in NVD database

Technical Details for CVE-2026-20543

Vulnerability Analysis

The vulnerability resides in the Modem component of affected MediaTek platforms. A logic error in how the modem handles or exposes internal state allows a locally authenticated process to read information it should not access. The result is confidentiality loss on the device, while integrity and availability remain unaffected.

The issue maps to [CWE-215], which covers sensitive information inadvertently exposed through debugging or diagnostic code paths. The Exploit Prediction Scoring System places this issue in a low exploitation-likelihood band, and no public proof-of-concept exploit or in-the-wild activity has been reported.

Root Cause

MediaTek describes the defect as a logic error in modem code. Such errors typically arise when a conditional check, state machine transition, or access decision does not correctly validate the context before returning data. In this case the flawed logic permits a local process to receive modem data that should be restricted to privileged components.

Attack Vector

Exploitation requires local access to the device and a process running with low privileges. The attacker invokes the vulnerable modem interface and receives sensitive data in response. No user interaction is needed, and the attacker does not gain code execution or elevated privileges through this flaw alone. Attackers can chain the disclosed information with other vulnerabilities to further compromise the device.

No verified exploit code is available. Refer to the MediaTek Security Bulletin - October 2026 for technical details.

Detection Methods for CVE-2026-20543

Indicators of Compromise

Unexpected processes querying modem interfaces or AT command endpoints from non-system UIDs.
Anomalous read patterns against modem diagnostic or debug channels on Android devices.
Mobile device logs showing repeated access to modem IPC endpoints by unprivileged applications.

Detection Strategies

Inventory MediaTek-based devices and compare installed security patch levels against the October 2026 bulletin.
Monitor mobile application behavior for abuse of modem-related system services or baseband diagnostic interfaces.
Correlate device telemetry against MediaTek patch IDs including MOLY01645293 to confirm remediation status.

Monitoring Recommendations

Enroll mobile fleets in a mobile threat defense or UEM platform that reports Android security patch levels.
Alert on sideloaded applications requesting telephony or modem-adjacent permissions beyond stated functionality.
Track MediaTek monthly security bulletins and ingest patch metadata into vulnerability management workflows.

How to Mitigate CVE-2026-20543

Immediate Actions Required

Apply the vendor patch once the OEM delivers an Android security update containing MediaTek patch MOLY01645293.
Restrict installation of untrusted applications on affected devices through enterprise mobility management policy.
Audit installed applications for unnecessary telephony, modem, or diagnostic permissions and remove non-essential ones.

Patch Information

MediaTek released the fix in its October 2026 Product Security Bulletin under Issue ID MSV-6761 with Patch ID MOLY01645293. OEMs integrate the modem patch into their Android security maintenance releases. Confirm installation by validating the device's reported Android security patch level after the OEM update.

Workarounds

Limit device enrollment to builds that include the October 2026 Android security patch level or later.
Disable developer options and USB debugging on production devices to reduce the local attack surface.
Enforce application allowlisting through UEM to block untrusted local processes capable of invoking modem interfaces.

bash

# Verify Android security patch level on a managed device
adb shell getprop ro.build.version.security_patch