CVE-2025-45985: B-link Bl-wr9000 Firmware RCE Vulnerability

CVE-2025-45985 Overview

CVE-2025-45985 is a critical command injection vulnerability affecting multiple B-Link router models. The vulnerability exists in the bs_SetSSIDHide function, which fails to properly sanitize user-supplied input before passing it to system commands. This allows unauthenticated remote attackers to execute arbitrary commands on the underlying operating system with root privileges.

Command injection vulnerabilities in IoT devices are particularly dangerous because these devices often operate with minimal security controls, lack logging capabilities, and may persist on networks unmonitored for extended periods. Successful exploitation of this vulnerability could allow attackers to establish persistent access, intercept network traffic, or pivot to other devices on the network.

Critical Impact

Unauthenticated remote attackers can execute arbitrary commands with root privileges on affected B-Link routers, potentially compromising entire network segments.

Affected Products

• B-Link BL-WR9000 Firmware v2.4.9
• B-Link BL-AC2100_AZ3 Firmware v1.0.4
• B-Link BL-X10_AC8 Firmware v1.0.5
• B-Link BL-LTE300 Firmware v1.2.3
• B-Link BL-F1200_AT1 Firmware v1.0.0
• B-Link BL-X26_AC8 Firmware v1.2.8
• B-Link BLAC450M_AE4 Firmware v4.0.0
• B-Link BL-X26_DA3 Firmware v1.2.7

Discovery Timeline

• 2025-06-13 - CVE-2025-45985 published to NVD
• 2025-07-10 - Last updated in NVD database

Technical Details for CVE-2025-45985

Vulnerability Analysis

This vulnerability is classified as CWE-77 (Improper Neutralization of Special Elements used in a Command), commonly known as command injection. The bs_SetSSIDHide function in the affected B-Link router firmware accepts user input that is subsequently incorporated into system shell commands without adequate sanitization or validation.

The network-accessible nature of this vulnerability means that any attacker who can reach the router's management interface can potentially exploit it. No authentication is required, and no user interaction is needed. The vulnerability affects the confidentiality, integrity, and availability of the device, as successful exploitation grants complete control over the router's operating system.

Router compromise at this level enables attackers to intercept all network traffic passing through the device, modify DNS settings to redirect users to malicious sites, create persistent backdoor access, or use the device as a launching point for attacks against other internal network resources.

Root Cause

The root cause of CVE-2025-45985 is insufficient input validation and sanitization in the bs_SetSSIDHide function. The function appears to accept parameters related to SSID visibility settings and constructs system commands using string concatenation without properly escaping or filtering shell metacharacters.

When user-controlled input containing shell metacharacters (such as ;, |, $(), or backticks) is passed to this function, these characters are interpreted by the shell, allowing attackers to inject and execute additional commands beyond the intended functionality.

Attack Vector

The attack is network-based and targets the router's web management interface. An attacker sends a specially crafted HTTP request to the vulnerable endpoint that handles SSID visibility settings. By embedding shell metacharacters and malicious commands within the request parameters, the attacker can cause the router to execute arbitrary commands.

The vulnerability allows attackers to chain commands using shell operators. For example, an attacker might append commands to download and execute a malicious script, create a reverse shell connection, or modify the router's configuration to establish persistent access. The commands execute with root privileges since the router firmware typically runs its web server and associated CGI scripts as the root user.

Technical details regarding the specific exploitation method can be found in the GitHub Command Injection Research documentation.

Detection Methods for CVE-2025-45985

Indicators of Compromise

• Unexpected outbound connections from router IP addresses to unknown external hosts
• Unusual processes or services running on the router that are not part of standard firmware
• Modified router configurations, particularly DNS settings, firewall rules, or port forwarding entries
• Evidence of command injection payloads in web server access logs containing shell metacharacters
• Newly created user accounts or SSH keys on the router

Detection Strategies

• Monitor network traffic for suspicious HTTP requests targeting B-Link router management interfaces containing shell metacharacters in parameters
• Implement network intrusion detection rules to identify common command injection patterns in traffic destined for IoT device management ports
• Deploy honeypot routers with vulnerable firmware versions to detect active exploitation attempts
• Review router configurations periodically for unauthorized changes that may indicate compromise

Monitoring Recommendations

• Establish baseline network behavior for all B-Link routers and alert on anomalies such as unusual traffic volumes or destinations
• Configure centralized logging for router management interface access where supported
• Monitor for DNS queries from router IP addresses that deviate from configured upstream DNS servers
• Implement egress filtering to detect and block unauthorized outbound connections from network infrastructure devices

How to Mitigate CVE-2025-45985

Immediate Actions Required

• Isolate affected B-Link routers from untrusted networks immediately by disabling remote management interfaces
• Restrict management interface access to trusted internal networks only using firewall rules or ACLs
• Check for firmware updates from B-Link and apply any available security patches
• Audit router configurations for signs of compromise and reset to factory defaults if suspicious changes are detected
• Consider replacing end-of-life devices that will not receive security updates

Patch Information

At the time of publication, no vendor advisory or patch information is available from B-Link. Organizations should monitor the B-Link website and support channels for security updates addressing CVE-2025-45985. Until patches are available, implementing network-level mitigations is critical.

Given the critical nature of this vulnerability and the high EPSS percentile (96.391%), indicating a significant likelihood of exploitation in the wild, organizations should prioritize mitigation efforts.

Workarounds

• Disable remote management access entirely and only allow management from directly connected devices
• Place vulnerable routers behind a separate firewall that restricts access to management interfaces
• Implement network segmentation to limit the impact of a compromised router on other network resources
• If the router supports it, enable access control lists to restrict management interface access to specific IP addresses
• Consider deploying a VPN to access router management interfaces rather than exposing them directly

# Example iptables rules to restrict router management access (apply on upstream firewall)
# Block external access to common router management ports
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 8080 -j DROP

# Allow management only from trusted admin workstation
iptables -I FORWARD -s 192.168.1.100 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT