Pierluigi Paganini August 23, 2023

Four vulnerabilities in the TP-Link Tapo L530E smart bulb and impacting the mobile app used to control them expose users to hack.

Researchers from the University of Catania (Italy) and the University of London (UK) have discovered four vulnerabilities impacting the TP-Link Tapo L530E smart bulb and the mobile app TP-Link’s Tapo app, which could allow attackers to steal the users’ WiFi password.

TP-Link Tapo L530E is one of the most popular smart bulbs on multiple marketplaces, including Amazon. The mobile application, TP-link Tapo, used to control the devices, is a smart device management app with 10 million installations on Play Store.

The first vulnerability is an improper authentication issue on Tapo L503E, an attacker can exploit the issue to impersonate the device during the session key exchange step.

The flaw can allow an adjacent attacker to retrieve Tapo user passwords and control Tapo devices. The vulnerability received a CVSS score of 8.8.

“Vulnerability 1. Lack of authentication of the smart bulb with the Tapo app, 8.8 CVSS score, High severity. The app does not get any guarantee about the identity of its peer. Therefore, anyone can authenticate to the app and pretend to be the smart bulb.” reads the research paper.

The vulnerability can only be exploited if the bulb is in setup mode, when it exposes its SSID. The researchers pointed out that even if it is already connected, the attacker can mount a Wi-Fi deauthentication attack and repeat it until the user resets the bulb.

The second flaw is related to the use, by the smart bulb and the Tapo app, of a hardcoded, short shared secret exposed by code fragments.

The flaw received a CVSS score of 7.6.

The third issue is a lack of randomness during symmetric encryption, the initialisation vectors (IVs) used by the Tapo app and the smart bulb are static, and each communication session uses a single, fixed IV for each message. The flaw received a CVSS score of 4.6. The fourth vulnerability is caused by insufficient message freshness by both the app and the smart bulb.

The attackers can also conduct a different attack, they can use the recently acquired credentials to mimic the user while configuring the light bulb. Using this trick the attacker can obtain a session key from the device, which can then be transmitted back to the user. As a result, the attacker successfully executes a man-in-the-middle attack. Furthermore, during the device setup process, the Tapo app inadvertently exposes Wi-Fi credentials to the attacker, significantly heightening the potential for malicious activities that rely on local access.

Upon exploiting the fourth vulnerability, the attacker is assured that whatever message he replays will be accepted by the smart bulb, creating the condition for a Denial-of-Service (DoS) attack.

The other issues can allow an attacker to retrieve the key used by the app and the smart bulb for authentication and message integrity verification, enabling them to manipulate the authentication procedure.

The researchers shared their findings with TP-Link through the company’s vulnerability reporting program. The vendor has started working to address the vulnerabilities.

“One way to interpret such findings could be that “small” IoT devices may have raised insufficient cybersecurity attention thus far, i.e., insufficient cybersecurity measures due to a preconception that they may not be worth hacking or exploiting. Our work pins down this preconception as wrong, at least because the scope of our attacks expands onto all devices of the Tapo family a victim may use and, most importantly, potentially onto the entire victim’s Wi-Fi network, which the attacker is enabled to penetrate.” concludes the paper. “While more and more experiments will certainly follow on similar bulbs and other inexpensive devices, we argue that the evidence we have gathered thus far is sufficient to call for a fuller application of a zero trust model to the IoT domain.”

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Pierluigi Paganini

(SecurityAffairs – hacking, smart bulb)