CVE-2026-0147

Executive Summary

CVE-2026-0147 is a critical remote code execution vulnerability in Samsung’s mfc_core_nal_q.c driver, specifically within the __mfc_core_nal_q_get_dec_metadata_sei_nal function. The flaw is an out-of-bounds write caused by a missing bounds check on a buffer used during SEI NAL unit metadata parsing. An unauthenticated attacker can trigger this remotely without user interaction, leading to full system compromise. No public exploit or patch is currently available, making this a high-priority zero-day for Samsung device owners.

Supply Chain & Package Security

This vulnerability resides in a proprietary Samsung kernel driver (MFC – Multi-Format Codec). It is not distributed via NPM, PyPI, Go, or Ruby registries. The risk is limited to Samsung devices with affected firmware versions.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Base Score: 9.8 (Critical)
• Attack Vector: Network (AV:N) – Exploitable remotely.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – Vulnerability does not cross trust boundaries.
• Confidentiality, Integrity, Availability Impact: High (C:H/I:H/A:H) – Full compromise.

Deep Dive & Mechanics

The vulnerability exists in the Samsung MFC (Multi-Format Codec) kernel driver, which handles video decoding. The function __mfc_core_nal_q_get_dec_metadata_sei_nal processes Supplemental Enhancement Information (SEI) NAL units from a video stream. SEI NAL units contain metadata such as picture timing, buffering periods, and user data.

Root Cause: The function fails to validate the size of the SEI payload before writing it into a fixed-size buffer. An attacker can craft a malicious video stream with an oversized SEI NAL unit, causing an out-of-bounds write on the kernel heap.

Exploitation Path:

1. The attacker sends a specially crafted video stream (e.g., via a web browser, media player, or network service) to a Samsung device.
2. The MFC driver parses the SEI NAL unit without checking its length against the destination buffer.
3. The out-of-bounds write corrupts adjacent kernel memory, potentially overwriting function pointers or data structures.
4. The attacker can then redirect execution flow to achieve arbitrary code execution in kernel context.

Impact: Full remote code execution with kernel privileges. The attacker can install malware, exfiltrate data, or render the device inoperable.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// mfc_core_nal_q.c
void __mfc_core_nal_q_get_dec_metadata_sei_nal(struct mfc_core_nal_q *nal_q, u8 *sei_data, u32 sei_len) {
    u8 metadata_buf[256]; // Fixed-size buffer
    // Missing bounds check: memcpy uses attacker-controlled sei_len
    memcpy(metadata_buf, sei_data, sei_len);
    // Process metadata...
}

Patched Code (Expected):

// mfc_core_nal_q.c
void __mfc_core_nal_q_get_dec_metadata_sei_nal(struct mfc_core_nal_q *nal_q, u8 *sei_data, u32 sei_len) {
    u8 metadata_buf[256];
    if (sei_len > sizeof(metadata_buf)) {
        // Reject oversized SEI NAL unit
        pr_err("SEI NAL unit too large: %u > %zu\n", sei_len, sizeof(metadata_buf));
        return;
    }
    memcpy(metadata_buf, sei_data, sei_len);
    // Process metadata...
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A Samsung device with an unpatched MFC driver (e.g., Galaxy S series, Note series).
• Ability to deliver a malicious video stream (e.g., via a web page, media file, or network service).

Exploitation Steps:

1. Craft Malicious Video: Use a tool like ffmpeg or a custom H.264/H.265 encoder to generate a video stream with an oversized SEI NAL unit. The SEI payload should contain shellcode or a ROP chain.
2. Deliver Payload: Host the video on a web server or embed it in a media file. When the victim’s device decodes the video, the vulnerability triggers.
3. Gain Kernel Code Execution: The out-of-bounds write overwrites a kernel function pointer (e.g., in a nearby struct). Redirect execution to a payload that escalates privileges or installs a backdoor.

Example Payload Structure (Conceptual):

# Python script to generate malicious SEI NAL unit
import struct

def craft_sei_nal(payload):
    # SEI NAL unit header: forbidden_zero_bit(1) + nal_unit_type(6) = 0x06 (SEI)
    nal_header = b'\x06'
    # SEI payload: payloadType (0) + payloadSize (attacker-controlled)
    payload_size = len(payload)
    sei_payload = b'\x00' + struct.pack('B', payload_size) + payload
    # RBSP trailing bits
    rbsp_trailing = b'\x80'
    return nal_header + sei_payload + rbsp_trailing

# Example shellcode (placeholder)
shellcode = b'\x90' * 1000  # NOP sled + actual shellcode
malicious_nal = craft_sei_nal(shellcode)

Blue Team (Defense & Detection)

Detection Strategy:

• Monitor for anomalous SEI NAL unit sizes in video streams.
• Use kernel memory integrity checks (e.g., KASLR, SMAP/SMEP) to mitigate exploitation.
• Deploy endpoint detection and response (EDR) agents that can detect kernel heap corruption.

Lab Setup:

• Use a Samsung device with a debug kernel (e.g., CONFIG_DEBUG_KERNEL=y).
• Enable kernel address sanitizer (KASAN) to detect out-of-bounds writes.
• Simulate the attack using a custom video player that sends oversized SEI NAL units.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Video streams with SEI NAL units exceeding 256 bytes.
  • Unusual RTP/RTSP streams containing malformed H.264/H.265 NAL units.
• Host IOCs:
  • Kernel crash logs (dmesg) showing __mfc_core_nal_q_get_dec_metadata_sei_nal with buffer overflow errors.
  • Unexpected kernel memory corruption in the MFC driver region.
  • Presence of unknown kernel modules or rootkits.
• File IOCs:
  • Media files with SEI NAL units larger than 256 bytes.
  • Suspicious video files with non-standard SEI payloads.

Detection Engineering

YARA Rule

rule CVE_2026_0147_SEI_Overflow {
    meta:
        description = "Detects oversized SEI NAL units in H.264/H.265 streams"
        author = "Valters IT"
        cve = "CVE-2026-0147"
    strings:
        $sei_header = { 06 } // NAL unit type 6 (SEI)
        $large_size = /[\x00-\xff]{257,}/ // SEI payload > 256 bytes
    condition:
        $sei_header at 0 and #large_size > 0
}

Sigma Rule

title: CVE-2026-0147 - Samsung MFC Driver SEI NAL Unit Overflow
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects kernel log entries indicating SEI NAL unit buffer overflow in Samsung MFC driver
author: Valters IT
logsource:
    product: linux
    service: kernel
detection:
    selection:
        - "mfc_core_nal_q: SEI NAL unit too large"
        - "mfc_core_nal_q: buffer overflow detected"
    condition: selection
falsepositives:
    - None expected
level: critical

Suricata Rule

alert ip any any -> any any (msg:"CVE-2026-0147 - Samsung MFC Driver SEI NAL Unit Overflow"; content:"|06|"; offset:0; depth:1; content:"|00|"; distance:1; within:1; byte_test:1,>,256,2; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Apply Vendor Patch: Monitor Samsung’s security bulletin for an official patch. Apply it as soon as available.
2. Disable MFC Driver: If not required, blacklist the mfc_core_nal_q kernel module using modprobe.blacklist=mfc_core_nal_q.
3. Network Filtering: Block or inspect video streams at the network perimeter for oversized SEI NAL units.

Long-Term Mitigations:

• Enable kernel hardening features (KASLR, SMAP, SMEP, CFI).
• Use a kernel with CONFIG_SLAB_FREELIST_RANDOM and CONFIG_SLAB_MERGE_DEFAULT=n to reduce heap exploitation reliability.
• Deploy an IDS/IPS with custom Suricata rules to detect exploitation attempts.

Workarounds:

• Disable hardware video decoding in browsers and media players until a patch is applied.
• Use software decoding (e.g., libavcodec) instead of the MFC driver.

Valters IT