CVE-2026-20476: CCCI Out of Bounds Read DoS Vulnerability

CVE-2026-20476 Overview

CVE-2026-20476 is an out-of-bounds read vulnerability in the MediaTek ccci (Cross Core Communication Interface) component. The flaw stems from a missing bounds check that allows a local attacker with low privileges to read outside allocated memory regions. Successful exploitation can trigger a local denial of service on affected MediaTek-based devices. User interaction is not required, but the attacker must already hold User execution privileges on the target device. MediaTek assigned Patch ID ALPS10981532 and Issue ID MSV-7660 to track the fix. The weakness is classified under CWE-787.

Critical Impact
A local, low-privilege application can crash the ccci subsystem, causing denial of service on the affected MediaTek chipset and disrupting cellular or inter-processor communication.

Affected Products

MediaTek chipsets running the ccci (Cross Core Communication Interface) driver
Android devices integrating vulnerable MediaTek baseband firmware
Specific product and version coverage is enumerated in the MediaTek Security Bulletin August 2026

Discovery Timeline

2026-08-03 - CVE-2026-20476 published to NVD
2026-08-03 - Last updated in NVD database

Technical Details for CVE-2026-20476

Vulnerability Analysis

The vulnerability resides in the MediaTek ccci driver, which mediates communication between the application processor and the modem processor on MediaTek platforms. A code path in the driver processes an input-controlled index or length value without validating it against the size of the underlying buffer. When the driver reads from the buffer using the unchecked value, it accesses memory beyond the allocation boundary.

The read touches unmapped or unrelated kernel memory, which forces the kernel to abort the operation and terminate the affected subsystem. Because the ccci driver runs in kernel context and mediates modem I/O, the fault propagates to a denial of service condition. Confidentiality and integrity are not affected because the vulnerability does not return the out-of-bounds data to userspace.

Root Cause

The root cause is a missing bounds check on an attacker-influenced value used to index into a fixed-size buffer inside the ccci driver. The defect maps to CWE-787 and is characteristic of driver code that trusts message metadata received from a lower-privileged component without revalidating length or offset fields before use.

Attack Vector

Exploitation is local. A malicious application with standard user privileges issues crafted requests to the ccci interface, triggering the out-of-bounds read from within kernel context. No user interaction is required, and no additional permissions beyond ordinary app execution are needed. The result is a kernel-side fault that produces denial of service on the device.

No public proof-of-concept, exploit-in-the-wild activity, or CISA KEV listing exists for this issue at time of writing. The EPSS score is 0.11%. See the MediaTek Security Bulletin August 2026 for authoritative technical detail.

Detection Methods for CVE-2026-20476

Indicators of Compromise

Recurrent kernel oops or panic entries referencing the ccci driver in dmesg or logcat kernel logs
Unexpected modem or radio interface resets on MediaTek-based devices
Repeated crashes of processes that interact with the ccci device nodes shortly after installing a new or unknown application

Detection Strategies

Aggregate Android crash and tombstone telemetry to identify clusters of ccci-related faults across a fleet
Correlate kernel panic timestamps with recent app installations to isolate the triggering package
Compare device firmware build fingerprints against MediaTek's fixed patch level published in the August 2026 bulletin

Monitoring Recommendations

Ingest mobile device management (MDM) crash and firmware inventory feeds into a central data lake for baseline comparison
Alert when devices report a MediaTek patch level older than the ALPS10981532 fix
Track installations of untrusted APKs on managed devices that subsequently produce baseband subsystem faults

How to Mitigate CVE-2026-20476

Immediate Actions Required

Inventory MediaTek-based devices in the environment and record their current security patch level
Restrict installation of untrusted applications on affected devices until the vendor patch is applied
Prioritize firmware updates for devices used by high-risk or privileged users

Patch Information

MediaTek addressed the issue under Patch ID ALPS10981532, tracked as Issue ID MSV-7660. The fix is distributed through device OEMs as part of the Android security patch cycle referenced in the MediaTek Security Bulletin August 2026. Apply the OEM firmware update that incorporates this patch as soon as it is available for each device model.

Workarounds

No vendor-supplied workaround exists; apply the OEM firmware update containing patch ALPS10981532
Enforce application allow-listing through MDM to reduce the local attack surface until patches are deployed
Disable sideloading and require Play Protect or equivalent scanning on managed devices

bash

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

# Compare the reported date against the MediaTek August 2026 bulletin
# Devices reporting a patch level earlier than the bulletin date remain exposed