CVE-2023-51773 – This vulnerability in BACnet Stack allows attac... (How to Fix)

Q: What is the severity of CVE-2023-51773?

CVE-2023-51773 has a CVSS score of 9.1 (CRITICAL). This vulnerability in BACnet Stack allows attackers to read beyond allocated memory boundaries in the bacapp_decode_application_data function. It affects systems using BACnet Stack versions before 1.3.2 for building automation and industrial control systems. Attackers could potentially leak sensitive information or cause denial of service.

📋 TL;DR

This vulnerability in BACnet Stack allows attackers to read beyond allocated memory boundaries in the bacapp_decode_application_data function. It affects systems using BACnet Stack versions before 1.3.2 for building automation and industrial control systems. Attackers could potentially leak sensitive information or cause denial of service.

💻 Affected Systems

Products:

BACnet Stack library
Products using BACnet Stack library

Versions: All versions before 1.3.2

Operating Systems: All platforms where BACnet Stack is used

Default Config Vulnerable: ⚠️ Yes

Notes: Affects any application using the vulnerable BACnet Stack library functions

📦 What is this software?

Bacnet Stack by Bacnetstack

View all CVEs affecting Bacnet Stack →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution leading to complete system compromise and lateral movement within building automation networks

🟠

Likely Case

Information disclosure of adjacent memory contents, potentially revealing sensitive data or causing application crashes

🟢

If Mitigated

Limited information leakage with no system compromise if proper network segmentation and access controls are implemented

🌐 Internet-Facing: MEDIUM - BACnet devices are often on internal networks but some may be exposed to internet

🏢 Internal Only: HIGH - BACnet networks often have poor segmentation and many vulnerable devices

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Buffer over-read vulnerabilities can be leveraged for information disclosure but require specific conditions for code execution

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 1.3.2

Vendor Advisory: https://github.com/bacnet-stack/bacnet-stack/blob/master/CHANGELOG.md

Restart Required: Yes

Instructions:

1. Update BACnet Stack to version 1.3.2 or later. 2. Recompile any applications using the library. 3. Restart affected services. 4. Verify the fix by checking version and testing functionality.

🔧 Temporary Workarounds

Network Segmentation

all

Isolate BACnet devices from untrusted networks and implement strict firewall rules

Access Control

all

Implement strict authentication and authorization for BACnet services

🧯 If You Can't Patch

Implement network segmentation to isolate BACnet devices from critical systems
Deploy intrusion detection systems to monitor for anomalous BACnet traffic

🔍 How to Verify

Check if Vulnerable:

Check if BACnet Stack version is below 1.3.2 in applications or check with package managers

Check Version:

Check application documentation or use 'strings' command on binaries to find BACnet Stack version

Verify Fix Applied:

Verify BACnet Stack version is 1.3.2 or later and test application functionality

📡 Detection & Monitoring

Log Indicators:

Application crashes
Memory access violations
Unusual BACnet traffic patterns

Network Indicators:

Malformed BACnet packets
Unusual BACnet port 47808 traffic
Repeated connection attempts to BACnet services

SIEM Query:

source="bacnet" AND (event_type="crash" OR error="memory" OR error="buffer")

📊 Metadata

CVE ID: CVE-2023-51773

CVSS v3 Score: 9.1 (CRITICAL)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

CWE: CWE-126

Published: February 29, 2024

Last Updated: May 23, 2025

🔗 References

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