External risk intelligence

Realtek SDK Web Server Vulnerability Enables Code Execution.

CVE advisoryKnown Exploit

CVE-2021-35395

This vulnerability affects an HTTP management interface within an SDK used for networking equipment such as access points and routers. These interfaces are commonly designed to be accessible via the network to facilitate device administration, making them typical examples of internet-facing or edge-reachable services.

Command Injection

Realtek Rtl819x Jungle Software Development Kit

2.0 to 3.4.14b

Halo Surface Signal: 5 out of 5 — more likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

The Realtek Jungle SDK provides an HTTP web server for configuring access points. This server contains flaws that allow for buffer overflows and command execution. Successful exploitation could permit remote attackers to gain control of the affected device.

Vulnerable SDK web server
Unsafe parameter copying
Arbitrary code execution

Attack Path

How an attacker could exploit the issue

The attack path begins with an exposed management interface within the Realtek Jungle SDK, which is used in networking equipment. Attackers can exploit vulnerabilities in this interface, such as insecure handling of user-supplied parameters, to execute arbitrary commands. This can lead to unauthorized control over the affected device.

Exposed network management interface.
Attacker sends crafted data.
Arbitrary command execution.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability presents a significant risk due to its potential for remote exploitation and severe impact. Attackers with advanced technical skills could leverage this vulnerability to execute arbitrary code on affected devices, potentially leading to widespread disruption. The ease of exploitation and the critical nature of the vulnerability warrant immediate attention to mitigate associated business risks.

Likely attacker skill level: Advanced
Required access or conditions: Network access
Business risk or urgency: Critical

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability, found in Realtek's Jungle SDK, affects the HTTP web server's management interface. Successful exploitation could allow remote attackers to execute arbitrary commands on affected devices, posing a significant business risk due to potential system compromise and data breaches. The exploitability and impact depend on how vendors have implemented the SDK.

Identify exposed network devices using the affected SDK.
Isolate or limit network access to these devices.
Apply vendor fixes, verify, and monitor.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

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Frequently asked questions

What is the Realtek Jungle SDK and what is it used for?

The Realtek Jungle SDK is a software development kit that provides an HTTP web server used for configuring access points and other networking equipment. It's a component that manufacturers integrate into their devices to allow for management and setup. The SDK includes web server binaries, one named webs and another named boa, which are susceptible to security flaws.

What kind of vulnerability does CVE-2021-35395 represent?

CVE-2021-35395 is a critical vulnerability that falls into the category of stack buffer overflows and arbitrary command execution. This means an attacker can send specially crafted input to the web server, causing it to overflow a buffer on the stack or execute arbitrary commands, potentially leading to a complete compromise of the device.

What are the preconditions for an attacker to exploit this vulnerability?

An attacker must have network access to the affected device. The vulnerability is triggered by sending specific, malformed data, particularly through parameters like 'submit-url', 'hostname', or 'peerPin' in the HTTP requests to the management interface. If these parameters are not handled safely, the buffer overflow or command injection can occur.

Who should be concerned about CVE-2021-35395 based on its exposure?

Organizations should be concerned if they use networking equipment that incorporates the Realtek Jungle SDK. The Halo Surface Signal indicates this vulnerability affects an HTTP management interface, which is typically accessible over the network, making it a potential target for external attackers.

What is the first step for managing this Realtek SDK vulnerability?

The initial step is to identify any network devices within your environment that utilize the affected Realtek Jungle SDK. Once identified, it's recommended to limit or isolate network access to these devices if possible, while actively seeking and applying any available patches or updates from the device vendor.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.