CVE-2020-24363: TP-link TL-WA855RE Missing Authentication for Critical Function Vulnerability

CVE-2020-24363 is a missing-authentication flaw in the TP-Link TL-WA855RE wireless range extender. An unauthenticated attacker already on the same local network can force a factory reset and reboot, then set a new administrative password and take control of the device. Because the product may be end-of-life or end-of-service, continued use leaves the device permanently exposed to this class of attack.

For IT and security teams the risk is straightforward: a compromised extender can serve as a foothold for further lateral movement, traffic interception, or persistent access on the LAN. Confirm all technical details against the vendor advisory before acting.

How it works

The vulnerability is classified as CWE-306 (Missing Authentication for Critical Function). The device accepts a TDDP_RESET POST request without requiring any credentials. An attacker who can reach the device on the local network simply submits that request; the extender performs a factory reset and reboots. Once the device is back online in its default state, the attacker can assign a new administrative password and thereby obtain full control.

No remote Internet exposure is required—only local-network reachability. The attack therefore depends on the attacker already being present on the same Layer-2 or Layer-3 segment (for example via a compromised client, guest Wi-Fi, or physical access). Specific request formats, ports, or firmware versions must be verified against the vendor advisory; public detail beyond the CISA summary is limited.

Am I affected? How to find it in your systems

The only product named in the advisory is the TP-Link TL-WA855RE range extender. These devices are typically deployed in homes, small offices, or branch locations to extend Wi-Fi coverage and appear on the network as wireless bridges or access points.

• Inventory all wireless extenders, bridges, and consumer-grade access points. Check device labels, DHCP leases, ARP tables, and network-management consoles for the model string “TL-WA855RE”.
• Confirm the exact firmware revision against the vendor advisory; the advisory notes that affected units may already be end-of-life or end-of-service.
• Look for unexpected factory-reset events, sudden loss of custom configuration, or administrative-password changes that were not performed by authorized staff. Syslog, SNMP traps, or management-console audit logs (if available) may record reboot or configuration-reset activity.
• Because the attack requires local-network access, also review recent wireless client associations and any rogue or guest devices that could have reached the extender.

If the model is present and no vendor patch is listed, treat the device as vulnerable.

How to remediate

The CISA-required action is to apply mitigations per vendor instructions or, if mitigations are unavailable, to discontinue use of the product. Given the end-of-life / end-of-service status noted in the advisory, the practical remediation path for most organizations is immediate decommissioning.

• Remove the TL-WA855RE from the network and replace it with a currently supported extender or access point that receives security updates.
• If a vendor firmware update exists for a still-supported revision, apply it only after confirming the fixed version in the official advisory.
• After removal or replacement, reset any credentials that may have been set on the compromised unit and re-validate the wireless network configuration.
• Document the change and update asset inventories so the model does not reappear.

Follow any additional guidance the vendor publishes; do not rely on community work-arounds that have not been validated.

If you can't patch immediately

When immediate replacement is not feasible, apply compensating controls that reduce the attack surface until the device can be retired.

• Segment the extender onto an isolated VLAN or guest network that has no route to sensitive internal resources. Restrict management-plane access to a jump host or management subnet only.
• Disable any remote-management or WAN-side administrative interfaces if they are enabled; the vulnerability is local, but reducing exposure still helps.
• Monitor for the TDDP_RESET POST request or for unexpected reboots and configuration resets. Alert on any administrative-password change that is not performed by authorized personnel.
• If a web-application firewall or network IPS is in the path, consider a temporary signature that blocks the known reset request pattern—confirm the exact pattern with the vendor advisory before deploying.
• Limit the number of clients that can associate with the extender and enforce strong wireless authentication so that an attacker cannot easily join the same network.

These measures only buy time; they do not eliminate the underlying missing-authentication flaw.

If your data may have been exposed

Actively exploited local-network vulnerabilities can lead to broader compromise of credentials, traffic, or adjacent systems. If you suspect the extender was reset or reconfigured by an unauthorized party, treat any credentials or sessions that traversed the device as potentially exposed. Rotate those credentials, review adjacent host logs for lateral movement, and consider a free exposure scan of organizational email addresses against known breach data sets to determine whether related accounts have already appeared in public dumps.