CVE-2025-53756 Overview
CVE-2025-53756 is a cleartext transmission vulnerability [CWE-319] affecting the Digisol DG-GR6821AC Router. The web management interface transmits authentication credentials without encryption. A remote attacker positioned to intercept network traffic can capture these credentials in plaintext. Successful exploitation grants unauthorized administrative access to the targeted device.
The issue was published to the National Vulnerability Database (NVD) on July 16, 2025 and is tracked under CERT-In Advisory CIVN-2025-0147. The vulnerability carries network attack vector characteristics with no required privileges or user interaction.
Critical Impact
Attackers intercepting traffic between administrators and the router web interface can capture credentials and take full control of the device, enabling traffic manipulation, DNS hijacking, and lateral movement into connected networks.
Affected Products
- Digisol DG-GR6821AC Router (web management interface)
- Firmware versions as listed in CERT-In Advisory CIVN-2025-0147
Discovery Timeline
- 2025-07-16 - CVE-2025-53756 published to NVD
- 2026-04-15 - Last updated in NVD database
Technical Details for CVE-2025-53756
Vulnerability Analysis
The Digisol DG-GR6821AC Router exposes a web management interface that transmits administrative credentials in cleartext. The login flow does not enforce Transport Layer Security (TLS), nor does it apply client-side encryption or hashing before transmission. Any party able to observe traffic between an administrator and the router can read the username and password directly from the wire.
The vulnerability is classified under [CWE-319]: Cleartext Transmission of Sensitive Information. Routers commonly serve their management UI over HTTP on the LAN side, which expands the threat surface to anyone connected to the local network, including guest Wi-Fi users, malicious devices, and attackers who have already established a foothold inside the perimeter.
Once credentials are captured, an attacker authenticates to the router as an administrator. From there, the attacker can modify firewall rules, change DNS settings, enable remote management, push malicious firmware, or pivot to attack devices on the internal network.
Root Cause
The root cause is the absence of encrypted transport for authentication traffic in the router's web management interface. Credentials submitted during login are sent as readable form parameters rather than being protected by TLS or another encryption layer.
Attack Vector
Exploitation requires network-adjacent or on-path access between the administrator and the router. Common scenarios include attackers connected to the same LAN segment, attackers performing ARP spoofing on local networks, and attackers who have compromised an upstream network device. The attacker passively captures HTTP traffic during an administrator login and extracts the credentials.
No verified public proof-of-concept code is associated with this CVE. The vulnerability mechanism is straightforward packet capture against unencrypted HTTP authentication traffic; see CERT-In Advisory CIVN-2025-0147 for vendor-specific details.
Detection Methods for CVE-2025-53756
Indicators of Compromise
- Unexpected administrator logins to the DG-GR6821AC web interface from unfamiliar source addresses
- Configuration changes such as modified DNS servers, new port forwards, or enabled remote management without authorized change records
- Firmware downgrade or unsigned firmware uploads via the management interface
Detection Strategies
- Inspect network captures on management VLANs for HTTP POST requests to router login endpoints containing plaintext username and password fields
- Alert on ARP table changes and gratuitous ARP traffic indicating possible man-in-the-middle activity against the router gateway
- Baseline router configuration files and trigger alerts when DNS, firewall, or remote-administration settings change outside of scheduled windows
Monitoring Recommendations
- Forward router syslog and authentication events to a centralized logging platform for retention and correlation
- Monitor for repeated failed logins followed by a successful login, which can indicate credential testing after capture
- Track outbound traffic from the router itself for connections to unexpected hosts that could indicate post-compromise command and control
How to Mitigate CVE-2025-53756
Immediate Actions Required
- Restrict access to the router web management interface to a dedicated management VLAN or trusted host
- Disable remote (WAN-side) management until a vendor fix is applied
- Rotate the router administrator password and any credentials reused elsewhere
- Review router configuration for unauthorized changes to DNS, firewall, and port-forwarding rules
Patch Information
Refer to CERT-In Advisory CIVN-2025-0147 for vendor remediation guidance. Apply firmware updates published by Digisol for the DG-GR6821AC as they become available.
Workarounds
- Administer the router only from a directly connected Ethernet port on an isolated segment to minimize sniffing exposure
- Place the router management interface behind a VPN and block HTTP management traffic on all other interfaces
- Replace the device with hardware that supports HTTPS-only management if a vendor patch is not provided
# Example: block HTTP management traffic from untrusted segments on an upstream firewall
iptables -A FORWARD -s 192.168.10.0/24 -d <router-ip> -p tcp --dport 80 -j DROP
iptables -A FORWARD -s 192.168.10.0/24 -d <router-ip> -p tcp --dport 443 -j ACCEPT
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
