CVE-2026-38571 Overview
CVE-2026-38571 affects the Tenda N300 F3 (V603) wireless router. The device exposes an unauthenticated Universal Asynchronous Receiver-Transmitter (UART) debug console on its serial interface. This console stores WPA2 credentials in cleartext and exposes rr (read register) and wr (write register) commands without authentication. A physically proximate attacker who connects to the serial header can extract stored WPA2 passphrases and perform arbitrary memory reads or writes. The weakness is classified as [CWE-312] Cleartext Storage of Sensitive Information.
Critical Impact
An attacker with physical access to the router serial console can recover WPA2 network credentials and read or modify device memory without authentication.
Affected Products
- Tenda N300 F3 wireless router
- Firmware version V603
- Devices exposing the internal UART debug header
Discovery Timeline
- 2026-06-26 - CVE-2026-38571 published to the National Vulnerability Database (NVD)
- 2026-06-29 - Last updated in NVD database
Technical Details for CVE-2026-38571
Vulnerability Analysis
The Tenda N300 F3 (V603) exposes a UART debug console accessible through the router's internal serial header. The console does not enforce authentication before granting command access. Two categories of weakness combine to enable exploitation.
First, the device stores the WPA2 pre-shared key in cleartext and returns it through console queries. This violates secure credential storage practices for sensitive network authenticators.
Second, the console exposes rr and wr primitives that permit direct memory read and write operations against arbitrary addresses. Without authentication, any operator connected to the UART pins can invoke these commands.
The attack requires physical proximity, which limits remote exploitation but remains relevant for supply chain, evil-maid, and lost-device scenarios. The Exploit Prediction Scoring System (EPSS) probability is low, reflecting the physical access requirement.
Root Cause
The root cause is dual. The firmware stores WPA2 credentials without encryption or protected storage. The debug console omits authentication and access control on privileged register commands. Debug interfaces intended for factory provisioning were left enabled in production firmware.
Attack Vector
An attacker opens the router chassis and connects to the UART header using a serial-to-USB adapter. The attacker then issues console commands to dump stored WPA2 credentials or execute rr/wr operations against target memory addresses. Refer to the GitHub CVE-2026-38571 PoC Repository for technical details on the console interaction sequence.
Detection Methods for CVE-2026-38571
Indicators of Compromise
- Physical tampering evidence on router enclosures, including opened cases, exposed screws, or attached serial adapters
- Unexpected WPA2 authentication events from previously unseen client devices on the wireless network
- Configuration drift or unexplained firmware behavior consistent with memory write activity through the UART console
Detection Strategies
- Perform periodic physical inspection of deployed Tenda N300 F3 routers for signs of chassis intrusion
- Monitor wireless authentication logs from upstream infrastructure for anomalous associations following physical maintenance windows
- Correlate network access anomalies with facility access logs to identify potential physical exploitation
Monitoring Recommendations
- Deploy tamper-evident seals on router enclosures and audit them on a defined schedule
- Rotate WPA2 pre-shared keys after any suspected physical access to the device
- Track wireless client MAC addresses and alert on new devices joining sensitive network segments
How to Mitigate CVE-2026-38571
Immediate Actions Required
- Restrict physical access to Tenda N300 F3 routers by placing them in locked enclosures or secured wiring closets
- Rotate WPA2 credentials on any device suspected of physical compromise
- Inventory affected devices and prioritize replacement for deployments in uncontrolled physical environments
Patch Information
No vendor patch is referenced in the NVD entry at the time of publication. Consult the GitHub CVE-2026-38571 PoC Repository and Tenda vendor advisories for any subsequent firmware updates addressing the debug console exposure.
Workarounds
- Deploy the router only in physically controlled environments where UART access is not feasible for untrusted parties
- Consider replacing affected units with hardware that disables debug interfaces in production firmware
- Apply tamper-evident seals to the router chassis and audit for signs of intrusion before returning any suspect device to service
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
