CVE-2020-24363 is a missing authentication for critical function vulnerability in TP-Link TL-WA855RE. CISA added it to the Known Exploited Vulnerabilities catalogue on 2 September 2025, which means attackers have used it in real attacks. TP-link TL-WA855RE contains a missing authentication for critical function vulnerability. The attacker can then obtain incorrect access control by setting a new administrative password.
What this vulnerability means in a router or range extender
A missing authentication for a critical function means the device exposes an administrative action without first proving the caller is authorised. In this case, the weakness lets an attacker reach a management function that should be protected, then set a new administrative password and take control of the device.
That is dangerous because small office and home networking gear often sits at the trust boundary for many users and devices. Once management access is gained, the attacker may be able to change security settings, redirect traffic, or use the device as a foothold for broader compromise.
Why this kind of flaw is high risk
The core issue is not just “weak login”, it is the absence of the check that decides whether a sensitive function should be available at all. When that check is missing, any path to the function becomes an attack path, especially if the device is internet exposed or reachable from an untrusted local network.
Attackers often look for these flaws because they are simple to exploit and can yield immediate administrative access. For a network device, that can turn a low-complexity bug into a high-impact compromise that affects confidentiality, availability and trust in the local network.
How organisations should assess exposure and verify compromise
Start by identifying every deployed instance of the exact model, then confirm whether any management interface is exposed beyond the intended management network. Review vendor advisories and the NIST National Vulnerability Database and CVE Program entry for authoritative vulnerability references and tracking.
If the device was exposed, assume configuration changes may have occurred even if users did not notice an outage. Check for altered admin credentials, unexpected DNS or routing settings, firmware changes, and unfamiliar remote-access or management options.
Remediation and control hardening
Patch or replace the affected device as soon as the vendor guidance allows, and remove any unnecessary management exposure in the meantime. The same discipline used for broader vulnerability handling also applies here, so the Vulnerability Management Guide is useful for prioritising scope, verification and remediation follow-up.
Where immediate replacement is not possible, restrict management to trusted networks, disable remote administration, and enforce strong administrative credentials. Treat the device as part of the organisation’s trust boundary, not as a consumer accessory, because its administrative plane can directly affect network security.
Detection and post-exploitation review
Look for signs that the admin password changed unexpectedly, especially if users report being locked out or settings have been reset. Also review logs, if available, for configuration changes that do not match planned maintenance, and inspect whether internet-facing management traffic has occurred.
If compromise is suspected, restore trusted configuration, rotate any credentials stored on or used with the device, and review adjacent systems for secondary access. A compromised edge device can be used to support persistence, traffic manipulation, or later movement into other internal assets.
Risk and Threat Considerations
This flaw creates direct administrative takeover risk because the attacker does not need to defeat normal login controls before reaching a critical function. On a device that routes or mediates local traffic, that can expose users to traffic interception, service disruption, or covert configuration tampering.
Failure mechanism: The management function accepts a password-setting action without first verifying that the caller is authorised to perform it, so the attacker can seize control through the intended admin path rather than bypassing it with a separate exploit.
Impact: A successful attacker can alter device settings, lock out legitimate administrators, and potentially use the device as a staging point for broader network abuse.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
CIS Controls v8, NIST SP 800-53 Rev 5 and OWASP ASVS set the technical controls, while ISO/IEC 27001:2022 defines the regulatory obligations.
| Framework | Control / Reference | Relevance |
|---|---|---|
| CIS Controls v8 | CIS-12 — Network Infrastructure Management | This flaw affects network-device administration and exposure. |
| Recommendation — Restrict management access and monitor network device configurations for unauthorized changes. | ||
| NIST SP 800-53 Rev 5 | AC-3 — Access Enforcement | The issue is unauthorized access to a critical administrative function. |
| CM-6 — Configuration Settings | The attack changes device settings and admin state. | |
| Recommendation — Enforce access checks on every administrative action before the device accepts a change. Baseline and verify approved configuration values to detect unauthorized administrative changes. | ||
| ISO/IEC 27001:2022 | A.8.20 — Network security | The term concerns protection of a networked device at its management boundary. |
| Recommendation — Secure the device management surface and limit exposure to trusted administrative paths. | ||
| OWASP ASVS | V8 — Authorization | The vulnerability is a missing check on a critical function before state change. |
| Recommendation — Require authorization checks on every sensitive action, including administrative password changes. | ||
Practitioner Guidance
Why practitioners should care: For network devices, administrative access is often equivalent to control over the local trust boundary. If the management plane can be reached without proper authentication, the exposure is operational, not just theoretical.
What to watch for: Treat unexpected password changes, configuration drift, and unapproved management exposure as compromise indicators. If the device is still in service, verify whether its admin interface is reachable from any network segment that should not be able to manage it.
Practitioner takeaway: When a router or extender loses its authentication gate, replace or isolate it quickly, then assume the configuration and adjacent traffic paths may already be untrusted.
Related resources from NHI Mgmt Group
- CVE-2025-32433 (Erlang Erlang/OTP SSH Server Missing Authentication for Critical Function)
- CVE-2023-28461 (Array Networks AG and vxAG ArrayOS Missing Authentication for Critical Function)
- CVE-2023-27532 (Veeam Backup & Replication Cloud Connect Missing Authentication for Critical Function)
- CVE-2026-20253 (Splunk Enterprise Missing Authentication for Critical Function)