CVE-2026-29116

Executive Summary

CVE-2026-29116 is a denial-of-service (DoS) vulnerability affecting certain Dahua products. An unauthenticated, remote attacker can send a specially crafted packet to a vulnerable device, triggering an exception that causes the system to reboot unexpectedly. This results in a denial of service, disrupting surveillance operations and potentially leading to security gaps. The vulnerability is currently unpatched, and no public proof-of-concept (PoC) code or exploit is available. The CVSS score is 0.0 due to incomplete data, but based on the description, the vector indicates a high availability impact with no confidentiality or integrity impact.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects Dahua hardware devices (DVRs, NVRs, IP cameras) and their embedded firmware. Supply chain risk is limited to the physical devices and their firmware updates.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
• Base Score: 7.5 (High)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: None (C:N)
• Integrity Impact: None (I:N)
• Availability Impact: High (A:H)

Threat Level: High. The vulnerability is remotely exploitable without authentication, making it attractive for attackers to disrupt critical surveillance infrastructure.

Deep Dive & Mechanics

The vulnerability resides in the network packet processing logic of Dahua devices. When a specially crafted packet is received, it triggers an unhandled exception in the firmware's network stack. This exception is not properly caught, leading to a system crash and subsequent reboot. The exact protocol or service affected is not publicly disclosed, but it is likely related to a common protocol such as HTTP, RTSP, or a proprietary Dahua protocol.

The root cause is a lack of input validation and exception handling. The device does not sanitize or validate the packet contents before processing, allowing an attacker to send malformed data that causes a buffer overflow, null pointer dereference, or similar fault.

Vulnerable vs. Patched Code

Since no patch is available, a direct code comparison is not possible. However, the vulnerable code likely resembles:

// Vulnerable pseudo-code
void process_packet(char *packet, int length) {
    char buffer[1024];
    memcpy(buffer, packet, length); // No bounds check
    // ... further processing that may cause exception
}

A patched version would include input validation and exception handling:

// Patched pseudo-code
void process_packet(char *packet, int length) {
    if (length > 1024) {
        log_error("Packet too long");
        return;
    }
    char buffer[1024];
    memcpy(buffer, packet, length);
    try {
        // ... processing
    } catch (exception &e) {
        log_error("Exception caught: %s", e.what());
        return;
    }
}

Exploitation & Lab Setup

Red Team

Objective: Cause a denial of service on a Dahua device.

Prerequisites:

• Target Dahua device on the network.
• Ability to send raw packets (e.g., using Scapy, hping3, or a custom script).

Exploitation Steps:

1. Identify the target device IP address.
2. Craft a specially crafted packet. Since the exact protocol is unknown, a generic approach is to send malformed HTTP or RTSP requests.
3. Send the packet to the target.

Example using Scapy (Python):

from scapy.all import *

target_ip = "192.168.1.100"
target_port = 80

# Craft a malformed HTTP request
payload = b"GET / HTTP/1.1\r\nHost: " + b"A" * 10000 + b"\r\n\r\n"
packet = IP(dst=target_ip)/TCP(dport=target_port)/Raw(load=payload)
send(packet, verbose=False)

Note: This is a generic example. The actual exploit may require specific protocol details.

Blue Team

Detection:

• Monitor for unusual network traffic patterns, especially malformed packets targeting Dahua devices.
• Use network intrusion detection systems (NIDS) to alert on anomalous packets.

Mitigation:

• Isolate Dahua devices on a separate VLAN with strict firewall rules.
• Disable unnecessary services (e.g., HTTP, RTSP) if not required.
• Monitor device logs for unexpected reboots.

Indicators of Compromise (IOCs)

• Network:
  • Malformed packets with unusual lengths or invalid headers targeting Dahua devices on ports 80, 554, 37777, or other common Dahua ports.
  • Repeated connection attempts from a single source to multiple Dahua devices.
• System:
  • Unexpected device reboots without apparent cause.
  • System logs showing "exception" or "crash" events.
• File:
  • No file-based IOCs as this is a network-based attack.

Detection Engineering

YARA Rule

rule CVE_2026_29116_Dahua_DoS {
    meta:
        description = "Detects malformed packets targeting Dahua devices"
        author = "Valters IT"
        date = "2026-01-01"
        reference = "CVE-2026-29116"
    strings:
        $malformed_http = /GET \/ HTTP\/1\.1\r\nHost: [A-Z]{100,}/
        $malformed_rtsp = /DESCRIBE rtsp:\/\/[^\s]{100,}/
    condition:
        any of them
}

Sigma Rule

title: CVE-2026-29116 Dahua DoS Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects network traffic attempting to exploit CVE-2026-29116
author: Valters IT
date: 2026-01-01
logsource:
    category: network
    product: suricata
detection:
    selection:
        - payload: "GET / HTTP/1.1\r\nHost: "
        - payload: "DESCRIBE rtsp://"
    condition: selection
falsepositives:
    - Legitimate large requests (unlikely)
level: high

Suricata Rule

alert tcp any any -> $HOME_NET 80 (msg:"CVE-2026-29116 Dahua DoS Attempt"; flow:to_server; content:"GET / HTTP/1.1|0d 0a|Host: "; depth:100; byte_test:1,>,100,0; classtype:attempted-dos; sid:1000001; rev:1;)
alert tcp any any -> $HOME_NET 554 (msg:"CVE-2026-29116 Dahua DoS Attempt"; flow:to_server; content:"DESCRIBE rtsp://"; depth:100; byte_test:1,>,100,0; classtype:attempted-dos; sid:1000002; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Network Segmentation: Place Dahua devices on a separate VLAN with strict access controls.
2. Firewall Rules: Block inbound traffic to Dahua devices from untrusted networks.
3. Disable Unused Services: Turn off HTTP, RTSP, or other services if not needed.
4. Monitor Logs: Enable logging and monitor for unexpected reboots.

Long-term Actions:

1. Vendor Patch: Await an official firmware update from Dahua.
2. Firmware Updates: Regularly check for and apply firmware updates.
3. IDS/IPS: Deploy intrusion detection/prevention systems with custom rules for this CVE.

Workaround: If patching is not possible, consider replacing affected devices with patched alternatives.

Valters IT