CVE-2025-8182: Tenda AC18 Firmware Auth Bypass Flaw

CVE-2025-8182 Overview

CVE-2025-8182 is a weak password requirements vulnerability [CWE-521] affecting the Tenda AC18 router running firmware version 15.03.05.19. The flaw resides in the Samba component configuration file located at /etc_ro/smb.conf. Attackers can target the device remotely over the network, though successful exploitation requires high attack complexity. The vulnerability has been publicly disclosed, increasing the risk of opportunistic abuse against exposed devices.

Critical Impact
Weak password policy in the Samba service of Tenda AC18 routers may allow remote attackers to compromise file-sharing access through credential-based attacks, exposing confidentiality, integrity, and availability of shared resources.

Affected Products

Tenda AC18 router (hardware)
Tenda AC18 firmware version 15.03.05.19
Samba component shipped via /etc_ro/smb.conf

Discovery Timeline

2025-07-26 - CVE-2025-8182 published to the National Vulnerability Database (NVD)
2026-04-29 - Last updated in NVD database

Technical Details for CVE-2025-8182

Vulnerability Analysis

The vulnerability stems from how the Tenda AC18 router configures its Samba file-sharing service. The configuration file /etc_ro/smb.conf enforces weak password requirements, allowing accounts with trivial or insufficiently strong credentials. This category of weakness is tracked under [CWE-521: Weak Password Requirements].

Attackers reachable over the network can target the Samba service with credential guessing or brute-force techniques. Because the password policy does not enforce sufficient complexity or length, the search space is reduced. Successful authentication grants access to Samba-exposed resources hosted by the router.

The vulnerability carries low impact across confidentiality, integrity, and availability, and the attack complexity is considered high. No authentication or user interaction is required at the network layer to attempt the attack.

Root Cause

The root cause is an insecure default configuration in the firmware-embedded Samba service. The /etc_ro/ directory holds read-only factory configuration on Tenda devices, meaning the weak policy is baked into the firmware image. Administrators cannot easily override the policy without firmware-level changes.

Attack Vector

The attack vector is network-based. An adversary with network reachability to the router's Samba listener attempts authentication using weak or common credentials permitted by the relaxed policy. Devices exposing SMB to untrusted networks face the highest risk, while LAN-only deployments narrow the exposure.

No verified exploit code or proof-of-concept has been published for this issue. See the VulDB entry for CVE-2025-8182 for additional technical context.

Detection Methods for CVE-2025-8182

Indicators of Compromise

Repeated failed SMB authentication attempts against the router's Samba service from external or unexpected internal hosts.
Successful SMB logons using short or dictionary-based passwords on Tenda AC18 devices.
Unusual file access patterns or large reads from shares exposed by the router.

Detection Strategies

Inventory all Tenda AC18 devices and confirm firmware version 15.03.05.19 is present.
Audit the contents of /etc_ro/smb.conf where access is available to verify the enforced password policy.
Scan the network perimeter for exposed SMB ports (TCP 139, 445) bound to router interfaces.

Monitoring Recommendations

Forward router and network telemetry to a centralized analytics platform for correlation of authentication anomalies.
Alert on brute-force authentication patterns targeting SMB services on embedded devices.
Track outbound SMB connections from the router that deviate from baseline behavior.

How to Mitigate CVE-2025-8182

Immediate Actions Required

Disable the Samba file-sharing feature on Tenda AC18 routers if not required for operations.
Block external access to SMB ports (TCP 139 and 445) at the network perimeter and ISP-facing interfaces.
Restrict Samba access to trusted internal segments using firewall rules or VLAN segmentation.
Replace any default Samba credentials with strong, unique passwords where the device permits configuration overrides.

Patch Information

No vendor patch has been referenced in the published CVE data. Monitor the Tenda official site for firmware updates addressing CVE-2025-8182.

Workarounds

Place affected routers behind a dedicated firewall that blocks inbound SMB traffic.
Use network access control lists to allow Samba connections only from authorized management hosts.
Retire the AC18 from internet-exposed roles and replace it with a device that enforces modern credential policies.

bash

# Example firewall rules to block SMB at the perimeter
iptables -A INPUT -p tcp --dport 139 -j DROP
iptables -A INPUT -p tcp --dport 445 -j DROP
iptables -A INPUT -p udp --dport 137 -j DROP
iptables -A INPUT -p udp --dport 138 -j DROP