CVE-2023-6334

Executive Summary

CVE-2023-6334 is a memory buffer overflow vulnerability in HYPR Workforce Access on Windows, affecting versions prior to 8.7. The vulnerability allows an authenticated local attacker to trigger a buffer overflow, potentially leading to denial of service or limited information disclosure. With a CVSS score of 5.3 (Medium), the risk is elevated due to the local attack vector and low complexity. No public exploit code or proof-of-concept is currently available, and the vendor has not released a patch. The EPSS score is 0.0%, indicating low exploitation activity in the wild.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a proprietary Windows application (HYPR Workforce Access) and does not involve open-source package supply chain risks.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
• Base Score: 5.3 (Medium)
• Attack Vector: Local (AV:L) – requires physical or remote desktop access to the system.
• Attack Complexity: Low (AC:L) – no special conditions needed.
• Privileges Required: Low (PR:L) – attacker needs a standard user account.
• User Interaction: None (UI:N) – no user action required.
• Scope: Unchanged (S:U) – vulnerability does not cross trust boundaries.
• Confidentiality Impact: Low (C:L) – limited data exposure possible.
• Integrity Impact: Low (I:L) – limited modification possible.
• Availability Impact: Low (A:L) – potential for service disruption.

Threat Level: Medium. The vulnerability is local and requires authentication, but the low complexity and lack of user interaction make it a viable target for privilege escalation or denial of service within an already compromised environment.

Deep Dive & Mechanics

The vulnerability is a classic buffer overflow (CWE-119) in the HYPR Workforce Access application for Windows. The software likely mishandles input data when processing authentication requests or session management, allowing an attacker to write data beyond the allocated buffer boundaries. This can corrupt adjacent memory, potentially leading to arbitrary code execution or application crashes.

Root Cause: Improper bounds checking on input data passed to a memory buffer. The application fails to validate the size of incoming data before copying it into a fixed-size buffer, enabling an overflow.

Attack Vector: An authenticated local user can craft a malicious input (e.g., a specially crafted authentication token or configuration file) that triggers the overflow when processed by the HYPR service.

Impact: Successful exploitation could allow the attacker to:

• Crash the HYPR service (denial of service).
• Execute arbitrary code in the context of the HYPR service (potentially SYSTEM privileges).
• Leak sensitive memory contents.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code remains in versions < 8.7. The patched version (8.7 or later) is expected to include proper input validation and bounds checking.

Vulnerable Code (Hypothetical Example):

void process_input(char *input) {
    char buffer[256];
    strcpy(buffer, input); // No bounds check
}

Patched Code (Expected):

void process_input(char *input) {
    char buffer[256];
    strncpy(buffer, input, sizeof(buffer) - 1);
    buffer[sizeof(buffer) - 1] = '\0';
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Windows system with HYPR Workforce Access < 8.7 installed.
• Local user account with standard privileges.

Steps:

1. Identify the vulnerable service (e.g., HYPRService.exe).
2. Craft a malicious payload that exceeds the expected buffer size (e.g., 300 bytes of data).
3. Deliver the payload via a local application or script that interacts with the HYPR service (e.g., via named pipe or API call).
4. Trigger the overflow to cause a crash or attempt code execution.

Example Payload (Python):

import socket

payload = b"A" * 300  # Overflow buffer
# Send to local HYPR service (hypothetical)
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("127.0.0.1", 8080))
s.send(payload)
s.close()

Note: No public exploit exists; this is a conceptual demonstration.

Blue Team (Detection & Defense)

Detection:

• Monitor for abnormal crashes of HYPRService.exe.
• Use Sysmon to log process creation and termination events.
• Enable Windows Event Logging for application crashes (Event ID 1000, 1001).

Defense:

• Apply the vendor patch when available.
• Restrict local user privileges to minimize attack surface.
• Use application whitelisting to prevent unauthorized executables.
• Enable DEP and ASLR for the HYPR service.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): None available (no known malicious samples).
• Process Names: HYPRService.exe (unusual crashes or high memory usage).
• Network Connections: Local connections to HYPR service ports (e.g., 8080, 8443).
• Event Logs: Windows Application Event Log entries with Event ID 1000 (Application Error) referencing HYPRService.exe.
• Registry Keys: None specific.

Detection Engineering

YARA Rule

rule CVE_2023_6334_HYPR_BufferOverflow {
    meta:
        description = "Detects potential buffer overflow exploitation attempts against HYPR Workforce Access"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2023-6334"
    strings:
        $s1 = "HYPRService.exe" ascii wide nocase
        $s2 = "buffer overflow" ascii wide nocase
        $s3 = "Access violation" ascii wide nocase
    condition:
        $s1 and ($s2 or $s3)
}

Sigma Rule

title: CVE-2023-6334 HYPR Workforce Access Buffer Overflow
id: 8a9b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects application crashes related to HYPR Workforce Access buffer overflow
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2023-6334
logsource:
    product: windows
    service: application
detection:
    selection:
        EventID: 1000
        ApplicationName: 'HYPRService.exe'
    condition: selection
falsepositives:
    - Legitimate application crashes due to other reasons
level: medium

Suricata Rule

alert tcp $HOME_NET any -> $HOME_NET 8080 (msg:"CVE-2023-6334 HYPR Workforce Access Buffer Overflow Attempt"; flow:to_server; content:"|41 41 41 41|"; depth:256; threshold:type limit, track by_src, count 1, seconds 60; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected systems if possible, until a patch is available.
2. Restrict local user privileges to prevent exploitation.
3. Monitor for abnormal behavior of HYPRService.exe using the provided detection rules.

Long-Term Fix:

• Apply the vendor patch (version 8.7 or later) as soon as it is released.
• Implement input validation and bounds checking in the application code.
• Conduct a security audit of the HYPR Workforce Access application.

Workarounds:

• Disable the HYPR service if not critical.
• Use application whitelisting to block unauthorized modifications.

Valters IT