Critical Web UI Vulnerabilities in Cisco Small Business IP Phones Allow Remote Code Execution and DoS

Cisco has disclosed multiple critical vulnerabilities affecting the web-based management interface of its Small Business SPA300 Series and SPA500 Series IP Phones. These high-severity flaws, tracked as CVE-2024-20450, CVE-2024-20451, CVE-2024-20452, CVE-2024-20453, and CVE-2024-20454, could allow unauthenticated remote attackers to execute arbitrary commands with root privileges or cause denial of service (DoS) conditions on vulnerable devices.

The vulnerabilities stem from improper validation of HTTP packets received by the web management interface. An attacker could exploit these flaws by sending specially crafted HTTP requests to a vulnerable device. Successful exploitation could lead to complete compromise of affected IP phones or disruption of voice communications.

With CVSS scores ranging from 7.5 to 9.8, these vulnerabilities pose a significant risk to organizations using the impacted Cisco Small Business IP phone models. Unfortunately, Cisco has announced that no patches will be released, as the affected devices have reached end-of-life status.

In this article, we'll examine the details of these critical web UI vulnerabilities, analyze their potential impact, and discuss mitigation strategies for organizations still using these legacy Cisco IP phone models.

A Short Introduction to Cisco Small Business SPA300 and SPA500 Series IP Phones

The Cisco Small Business SPA300 and SPA500 Series IP Phones are Voice over IP (VoIP) devices designed for small to medium-sized businesses. These phones offer a range of features to enhance communication and productivity in office environments.

Key features of these IP phone series include:

The SPA300 Series includes entry-level models suitable for common areas or light-use scenarios, while the SPA500 Series offers more advanced features for knowledge workers and busier environments. Both series were popular choices for businesses looking to deploy cost-effective VoIP solutions.

However, it's important to note that these phone models have reached end-of-life status. Cisco has announced the end of sale and support for these devices, recommending customers migrate to newer IP phone models for continued support and security updates.

Overview of the Vulnerabilities

On August 7, 2024, Cisco published a security advisory detailing five high-severity vulnerabilities in the web UI of certain Small Business IP phone models:

These vulnerabilities stem from improper processing of HTTP packets in the web-based management interface of affected devices. The flaws can be exploited by sending crafted HTTP requests to vulnerable IP phones, potentially allowing attackers to execute arbitrary commands with root privileges or cause devices to reload unexpectedly.

Affected Products

These vulnerabilities impact the following Cisco Small Business IP Phone models:

All software versions running on these phone models are affected, regardless of configuration.

Technical Details

Arbitrary Command Execution Vulnerabilities

CVE-2024-20450, CVE-2024-20452, and CVE-2024-20454 are buffer overflow vulnerabilities that could allow an unauthenticated remote attacker to execute arbitrary commands on the underlying operating system with root privileges.

The flaws exist because incoming HTTP packets are not properly validated for errors, which can result in a buffer overflow condition. By sending a crafted HTTP request to an affected device, an attacker could overflow an internal buffer and execute arbitrary commands at the root privilege level.

These vulnerabilities have been assigned a Critical severity rating with a CVSS base score of 9.8. The CVSS vector string is:

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

This indicates:

Successful exploitation would give an attacker full control over the vulnerable IP phone device.

Denial of Service Vulnerabilities

CVE-2024-20451 and CVE-2024-20453 are denial of service vulnerabilities that could allow an unauthenticated remote attacker to cause an affected device to reload unexpectedly.

These flaws also stem from improper validation of HTTP packets. An attacker could trigger a DoS condition by sending a specially crafted HTTP packet to the web interface of a vulnerable phone.

The DoS vulnerabilities have been rated High severity with a CVSS base score of 7.5. The CVSS vector string is:

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

This indicates:

A successful exploit could cause the IP phone to crash and reload, disrupting voice communications.

Root Cause Analysis

The root cause of these vulnerabilities appears to be insufficient input validation and error checking on HTTP requests received by the web management interface of affected IP phones.

Specifically, the flaws exist because:

This lack of robust input sanitization allows malformed HTTP packets to trigger buffer overflow conditions or unexpected device behavior.

The vulnerabilities likely stem from legacy code that was not developed with modern security best practices in mind. As these are older Small Business IP phone models, the embedded software may not have undergone rigorous security testing or code auditing.

Potential Impact

Successful exploitation of these vulnerabilities could allow an attacker to:

Given that these are network-connected VoIP phones, a large-scale attack could significantly impact business communications and operations.

The arbitrary command execution flaws (CVE-2024-20450, CVE-2024-20452, CVE-2024-20454) are particularly concerning, as they provide attackers with root-level access. This essentially gives complete control over vulnerable devices.

Even the DoS vulnerabilities (CVE-2024-20451, CVE-2024-20453) could have major operational impacts by taking phone systems offline.

Detecting Vulnerable Devices

To identify if your environment has vulnerable Cisco Small Business IP phones, take the following steps:

Unfortunately, Cisco has not provided specific affected software version information. The advisory states that all versions running on SPA300 and SPA500 Series phones are impacted.

Mitigations and Workarounds

Cisco has not released any software updates to address these vulnerabilities. Additionally, there are no workarounds available to mitigate the flaws.

This is because the affected SPA300 and SPA500 Series IP phone models have reached end-of-life status. Cisco will not be developing or releasing any further software updates for these legacy devices.

Given the lack of patches or workarounds, organizations still using these vulnerable IP phone models should consider the following risk mitigation strategies:

Conclusions

The discovery of multiple critical vulnerabilities in legacy Cisco Small Business IP phones highlights several important security lessons:

Organizations still using vulnerable Cisco SPA300 and SPA500 Series IP phones should treat replacing these devices as a high priority. In the interim, restricting network access and monitoring for suspicious activity is strongly recommended.

These types of critical flaws in VoIP phones and other network-connected devices underscore the importance of maintaining an accurate IT asset inventory and having a defined lifecycle management process. Proactively upgrading legacy systems is key to reducing organizational attack surface.

By staying on top of vendor security advisories and end-of-life announcements, companies can better plan for hardware/software upgrades before products lose support. This helps avoid situations where critical vulnerabilities are discovered in devices that can no longer be patched.

We hope this post helps you know about recently published security advisories for the web-based management interface of its Small Business SPA300 Series and SPA500 Series IP Phones. Thanks for reading this post. Please share this post and help secure the digital world.Visit our website thesecmaster.com, and our social media page on Facebook, LinkedIn, Twitter, Telegram, Tumblr, Medium, and Instagram and subscribe to receive updates like this.

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