CVE-2026-23789: Samsung Exynos MFC Use-After-Free Flaw

CVE-2026-23789 Overview

CVE-2026-23789 is a double-free vulnerability [CWE-415] in the Multi-Format Codec (MFC) encoder driver used by Samsung Exynos Mobile and Wearable Processors. The flaw stems from improper cleanup of dma_buf references during error handling paths in the kernel driver. Attackers with local low-privileged access can trigger kernel memory corruption and potentially achieve arbitrary code execution. The vulnerability affects a broad range of Exynos application processors and wearable chipsets shipped in Samsung devices.

Critical Impact
Successful exploitation leads to kernel memory corruption, privilege escalation to kernel context, and potential arbitrary code execution on affected Samsung Exynos-based devices.

Affected Products

Samsung Exynos Mobile Processors: 850, 1080, 2100, 1280, 2200, 1330, 1380, 1480, 2400, 1580, 2500, 2600, 1680
Samsung Wearable Processors: W920, W930, W1000
Devices shipping the affected MFC encoder kernel driver

Discovery Timeline

2026-09-14 - CVE-2026-23789 published to NVD
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-23789

Vulnerability Analysis

The vulnerability resides in the Exynos MFC encoder driver, which handles hardware-accelerated video encoding. The driver imports and manages dma_buf file descriptors passed from user space to share buffers between the userland application and the video hardware. During error handling in the buffer setup or configuration path, the driver releases the same dma_buf reference twice, causing a classic double-free condition on kernel-managed memory.

Because dma_buf structures maintain reference counts and are backed by heap allocations shared with the kernel's DMA subsystem, freeing them twice corrupts the kernel heap. An attacker who can influence subsequent allocations can reclaim the freed memory with controlled data, laying the groundwork for kernel arbitrary read/write primitives and code execution in kernel context.

Root Cause

The root cause is improper resource cleanup in an error path within the MFC encoder driver. When an operation fails after a dma_buf reference has been acquired, both the error handler and the normal cleanup routine release the same reference. This violates the reference-counted lifecycle expected by the DMA buffer sharing framework, producing the double-free tracked as [CWE-415].

Attack Vector

Exploitation requires local access with low privileges. An attacker executes a crafted user-space process that opens the MFC video device node (commonly /dev/video*) and issues ioctl calls to the encoder to trigger the vulnerable error path. Because the scope is Changed, successful exploitation can impact components beyond the driver itself, including kernel subsystems and other processes. No user interaction is required. Refer to the Samsung CVE-2026-23789 advisory for vendor technical details.

Detection Methods for CVE-2026-23789

Indicators of Compromise

Unexpected kernel panics, oops messages, or SLUB/SLAB corruption warnings referencing dma_buf, videobuf2, or the MFC driver in dmesg
Repeated abnormal termination of processes interacting with /dev/video* device nodes
Unprivileged processes invoking uncommon ioctl sequences on MFC encoder device nodes

Detection Strategies

Enable kernel hardening telemetry such as KASAN, KFENCE, or SLUB debug on test builds to catch double-free conditions during QA and threat hunts
Correlate crash telemetry from Android tombstones and dropbox with process access to Exynos MFC device nodes
Alert on non-media user IDs opening /dev/video* or issuing V4L2 encoder ioctls

Monitoring Recommendations

Forward Android kernel crash logs and SELinux denials to a centralized data lake for retrospective analysis
Monitor for privilege escalation indicators such as unexpected UID transitions or new root-owned processes on managed mobile devices
Track patch level compliance across the mobile fleet against Samsung Semiconductor security update bulletins

How to Mitigate CVE-2026-23789

Immediate Actions Required

Apply the vendor security update from Samsung Semiconductor as soon as it is available for the affected Exynos SoC
Inventory managed mobile and wearable devices to identify assets running affected Exynos processors
Restrict installation of untrusted applications that could invoke the MFC encoder interface

Patch Information

Samsung has published details for this vulnerability on its product security updates portal. Refer to the Samsung Semiconductor Product Security Updates page and the CVE-2026-23789 advisory page for firmware and driver update guidance. Device OEMs must integrate the fix and deliver it through their normal Android security patch level (SPL) channels.

Workarounds

Enforce mobile application allowlisting through MDM to block untrusted apps that could reach the MFC device interface
Ensure SELinux is in enforcing mode so that only media framework processes can access /dev/video* nodes
Restrict sideloading and developer mode on managed devices until the patch is applied

bash

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

# Confirm SELinux is in enforcing mode
adb shell getenforce

# List processes with access to MFC video device nodes
adb shell "ls -lZ /dev/video*"