CVE-2023-51608

Executive Summary

CVE-2023-51608 is a critical memory corruption vulnerability in Kofax Power PDF’s J2K file parsing engine. The flaw allows remote attackers to execute arbitrary code in the context of the current process, requiring user interaction (opening a malicious file or visiting a malicious page). The vulnerability stems from improper validation of user-supplied data, leading to a memory corruption condition. With a CVSS score of 7.8, this vulnerability poses a significant risk to enterprise environments using Kofax Power PDF for document processing. No public exploit code or patch details are currently available, but the risk is elevated due to the potential for weaponization in targeted attacks.

CVSS Breakdown & Threat Level

• CVSS Score: 7.8 (High)
• Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
• Attack Vector: Local (requires user to open a malicious file)
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

Threat Level: High. The vulnerability is exploitable with low complexity and no privileges, but requires user interaction. Successful exploitation leads to full compromise of the affected system.

Deep Dive & Mechanics

The vulnerability resides in the parsing of J2K (JPEG 2000) files within Kofax Power PDF. The specific flaw is a memory corruption caused by improper validation of user-supplied data during the parsing process. When a specially crafted J2K file is opened, the parser fails to properly check bounds or validate data structures, leading to a write-what-where condition. This allows an attacker to overwrite critical memory regions, such as function pointers or return addresses, and redirect execution flow to arbitrary code.

The attack surface is limited to user interaction, but the widespread use of PDF software in enterprise environments makes this a viable vector for phishing campaigns or drive-by downloads. The vulnerability is classified under CWE-787 (Out-of-bounds Write), indicating a classic buffer overflow or heap corruption scenario.

Vulnerable vs. Patched Code

No patch details are available. The vulnerable code is in the J2K parsing module of Kofax Power PDF. A hypothetical patched version would include additional validation checks for J2K data structures, such as:

• Vulnerable: Directly copying user-supplied data into a fixed-size buffer without length checks.
• Patched: Implementing bounds checking and using safe memory copy functions (e.g., memcpy_s).

Example of vulnerable pseudo-code:

void parse_j2k_data(char *input, size_t input_len) {
    char buffer[256];
    memcpy(buffer, input, input_len); // No bounds check
}

Example of patched pseudo-code:

void parse_j2k_data(char *input, size_t input_len) {
    char buffer[256];
    if (input_len > sizeof(buffer)) {
        // Handle error
        return;
    }
    memcpy(buffer, input, input_len);
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Kofax Power PDF (vulnerable version)
• A crafted J2K file with malicious payload

Exploitation Steps:

1. Create a malicious J2K file that triggers the memory corruption.
2. Deliver the file via email or web download.
3. When the target opens the file in Kofax Power PDF, the exploit triggers arbitrary code execution.

Example Payload Generation (conceptual):

# This is a conceptual example; no public exploit exists.
import struct

def create_malicious_j2k():
    # Craft a J2K file with oversized data to trigger overflow
    payload = b"A" * 256  # Padding
    payload += struct.pack("<I", 0xdeadbeef)  # Overwrite return address
    # Additional shellcode would be appended
    return payload

with open("malicious.j2k", "wb") as f:
    f.write(create_malicious_j2k())

Blue Team

Detection:

• Monitor for unusual J2K file downloads or email attachments.
• Use endpoint detection rules to flag Kofax Power PDF crashes or memory corruption events.

Hunting:

• Search for processes (e.g., PowerPDF.exe) with high memory usage or abnormal termination.
• Analyze crash dumps for signs of heap corruption.

Indicators of Compromise (IOCs)

• File Hashes: (None publicly available; would be generated from malicious J2K files)
• Network Indicators: Connections to unknown IPs post-exploitation (e.g., for C2)
• Process Anomalies: PowerPDF.exe crashing or spawning child processes (e.g., cmd.exe, powershell.exe)
• Registry Changes: Unauthorized modifications to HKLM\Software\Kofax\PowerPDF

Detection Engineering

YARA Rule

rule CVE_2023_51608_J2K_Memory_Corruption {
    meta:
        description = "Detects malicious J2K files targeting CVE-2023-51608"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2023-51608"
    strings:
        $j2k_magic = { FF 4F FF 51 }  // J2K file magic bytes
        $overflow_pattern = /.{256,}/  // Large data block
    condition:
        $j2k_magic at 0 and #overflow_pattern > 0
}

Sigma Rule

title: Kofax Power PDF J2K Memory Corruption Exploit
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects potential exploitation of CVE-2023-51608 via process crash or abnormal behavior
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\PowerPDF.exe'
        CommandLine|contains: '.j2k'
    condition: selection
falsepositives:
    - Legitimate J2K file processing
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2023-51608 J2K File Download"; flow:to_server,established; content:"|FF 4F FF 51|"; depth:4; fileext:"j2k"; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

• Patch: No official patch available. Monitor vendor advisories for updates.
• Mitigation:
  • Disable J2K file parsing in Kofax Power PDF if not required.
  • Use application whitelisting to prevent execution of untrusted PDF files.
  • Implement endpoint detection and response (EDR) to monitor for exploitation attempts.
  • Train users to avoid opening suspicious files or links.
• Workaround: Convert J2K files to other formats before opening in Kofax Power PDF.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert