CVE-2026-5363: TP-Link Archer C7 Information Disclosure

CVE-2026-5363 Overview

CVE-2026-5363 is an Inadequate Encryption Strength vulnerability affecting the TP-Link Archer C7 router versions v5 and v5.8, specifically within the uhttpd modules. The web interface encrypts the administrator password client-side using RSA-1024 before transmitting it to the router during the login process. This weak encryption implementation creates a significant security risk for network environments where the router is deployed.

An adjacent attacker with the ability to intercept network traffic could potentially perform a brute-force or factorization attack against the 1024-bit RSA key to recover the plaintext administrator password. Successful exploitation leads to unauthorized access and full compromise of the device configuration, allowing attackers to modify router settings, redirect traffic, or establish persistent backdoor access.

Critical Impact

Attackers on the adjacent network can recover administrator credentials through cryptographic attacks against weak RSA-1024 encryption, leading to complete device compromise.

Affected Products

• TP-Link Archer C7 v5 through Build 20220715
• TP-Link Archer C7 v5.8 through Build 20220715
• TP-Link Archer C7 uhttpd modules

Discovery Timeline

• 2026-04-16 - CVE CVE-2026-5363 published to NVD
• 2026-04-16 - Last updated in NVD database

Technical Details for CVE-2026-5363

Vulnerability Analysis

This vulnerability stems from the use of cryptographically weak RSA-1024 encryption for protecting administrator credentials during the login process. The 1024-bit RSA key size has been considered deprecated for security-critical applications since 2013, as computational advances have made factorization attacks increasingly feasible.

The affected uhttpd modules in the TP-Link Archer C7 router perform client-side password encryption before transmission. While this approach attempts to protect credentials in transit, the reliance on RSA-1024 undermines the security objective. An attacker positioned on the adjacent network—such as another device on the same LAN segment or a compromised wireless client—can capture the encrypted authentication traffic.

Once captured, the attacker can attempt offline cryptographic attacks against the weak RSA key. Modern computing resources, including cloud-based GPU clusters, have significantly reduced the time and cost required to factor 1024-bit RSA keys. Successful key factorization allows the attacker to decrypt all intercepted authentication attempts, revealing plaintext administrator passwords.

Root Cause

The root cause is classified under CWE-326 (Inadequate Encryption Strength). The TP-Link Archer C7 firmware implements RSA-1024 for client-side password encryption, a key size that no longer provides adequate security margins against modern cryptanalytic capabilities. Industry standards now mandate a minimum of RSA-2048 for secure communications, with RSA-3072 or RSA-4096 recommended for long-term security.

The vulnerability persists across firmware builds up to and including Build 20220715, indicating that the weak cryptographic implementation was not addressed in multiple firmware revisions.

Attack Vector

The attack requires adjacent network access, meaning the attacker must be positioned on the same network segment as the target router. This could be achieved through:

• Physical connection to the same LAN
• Association with the router's wireless network
• Compromise of another device on the same network segment

The attacker passively captures encrypted login traffic between legitimate users and the router's web interface. The captured RSA-encrypted password data is then subjected to offline factorization attacks. No user interaction is required beyond normal authentication activity, and the attack can be performed without generating suspicious network traffic that might trigger security alerts.

The technical complexity of the attack is high due to the computational requirements for RSA-1024 factorization, but dedicated attackers with sufficient resources can achieve successful key recovery.

Detection Methods for CVE-2026-5363

Indicators of Compromise

• Unexpected changes to router configuration settings or firewall rules
• Unknown administrator sessions or login attempts in router logs
• Modifications to DNS settings, routing tables, or port forwarding rules
• Presence of unauthorized wireless clients or DHCP reservations

Detection Strategies

• Monitor for unusual network traffic patterns targeting the router's web interface on adjacent network segments
• Implement network segmentation to isolate management interfaces from general user traffic
• Review router access logs for authentication attempts from unexpected internal IP addresses
• Deploy network intrusion detection systems (NIDS) to identify potential credential harvesting activities

Monitoring Recommendations

• Enable and regularly review authentication logs on the affected TP-Link Archer C7 devices
• Implement alerting for configuration changes to the router's administrative settings
• Monitor for traffic analysis attempts or ARP spoofing activities on the local network that could indicate an attacker positioning for credential interception
• Consider deploying a separate management VLAN with restricted access for router administration

How to Mitigate CVE-2026-5363

Immediate Actions Required

• Check the current firmware version and update to the latest available firmware from TP-Link
• Restrict web interface access to trusted management stations using firewall rules
• Consider disabling remote web management if not required
• Implement strong, unique administrator passwords that are rotated regularly
• Segment the network to limit adjacent network access to critical infrastructure

Patch Information

TP-Link has published information regarding this vulnerability. Administrators should consult the TP-Link FAQ for the latest firmware updates and security guidance. Ensure that firmware is updated to a version that addresses the weak RSA-1024 encryption implementation.

Workarounds

• Use SSH or other secure management protocols instead of the web interface where available
• Implement MAC address filtering and wireless client isolation to limit adjacent network attack surface
• Deploy a VPN for administrative access to the router's management interface
• Consider placing the router behind a more secure perimeter device that can provide additional authentication layers
• Monitor the network for unauthorized devices that could be used for traffic interception

# Configuration example
# Restrict web management access to specific IP addresses
# Access via SSH to configure if available, or through the web interface:
# 1. Navigate to Advanced > System Tools > Administration
# 2. Enable "Local Management" restrictions
# 3. Add trusted management IP addresses only
# 4. Disable "Remote Management" if not required
# 5. Consider changing the default management port from 80/443