CVE-2024-20454 Overview
CVE-2024-20454 is a critical buffer overflow vulnerability affecting the web-based management interface of Cisco Small Business SPA300 Series and SPA500 Series IP Phones. The vulnerability allows an unauthenticated, remote attacker to execute arbitrary commands on the underlying operating system with root privileges by sending specially crafted HTTP requests to vulnerable devices.
The flaw exists because incoming HTTP packets are not properly validated for errors, enabling attackers to overflow an internal buffer and gain complete control over affected IP phone devices. This represents a severe risk for organizations using these devices in their VoIP infrastructure.
Critical Impact
Unauthenticated remote attackers can achieve full root-level command execution on affected Cisco IP phones by exploiting improper HTTP packet validation, potentially compromising entire VoIP communication infrastructure.
Affected Products
- Cisco SPA300 Series IP Phones (SPA301, SPA303) - All firmware versions
- Cisco SPA500 Series IP Phones (SPA501G, SPA502G, SPA504G, SPA508G, SPA509G, SPA512G, SPA514G, SPA525G, SPA525G2) - All firmware versions
- Cisco Small Business IP Phone firmware across all affected product lines
Discovery Timeline
- August 7, 2024 - CVE-2024-20454 published to NVD
- August 23, 2024 - Last updated in NVD database
Technical Details for CVE-2024-20454
Vulnerability Analysis
This vulnerability is classified as CWE-120 (Buffer Copy without Checking Size of Input), commonly known as a classic buffer overflow. The web-based management interface of affected Cisco SPA IP phones fails to properly validate the size of incoming HTTP request data before copying it into fixed-size internal buffers.
When the web server component receives an HTTP request, it processes the packet contents without adequately checking for malformed or oversized input data. This absence of proper bounds checking allows an attacker to submit HTTP requests containing payloads that exceed the expected buffer boundaries.
The exploitation requires no authentication, meaning any attacker with network access to the device's management interface can attempt to exploit this vulnerability. Successful exploitation results in arbitrary command execution with root privileges, giving the attacker complete control over the device.
Root Cause
The root cause of CVE-2024-20454 lies in the improper handling of HTTP request data within the web-based management interface. The vulnerable code copies HTTP packet data into internal buffers without verifying that the input size does not exceed the allocated buffer capacity.
This classic buffer overflow pattern occurs when the application uses unsafe memory copy operations that do not enforce boundary checks. The lack of input validation allows attackers to write beyond the intended buffer boundaries, potentially overwriting critical memory structures such as return addresses or function pointers on the stack.
Attack Vector
The attack vector for CVE-2024-20454 is network-based, requiring no user interaction or authentication. An attacker can exploit this vulnerability by:
- Identifying a vulnerable Cisco SPA300 or SPA500 Series IP phone with an accessible web management interface
- Crafting a malicious HTTP request containing an oversized payload designed to overflow the target buffer
- Sending the crafted HTTP request to the device's management interface
- Achieving code execution when the buffer overflow corrupts memory and redirects execution flow
- Executing arbitrary commands with root privileges on the underlying operating system
The attack can be conducted remotely against any exposed device, making internet-facing or poorly segmented VoIP infrastructure particularly vulnerable.
Detection Methods for CVE-2024-20454
Indicators of Compromise
- Unusual or malformed HTTP requests targeting Cisco SPA IP phone management interfaces on common ports (typically port 80 or 443)
- Unexpected process execution or system commands running on IP phone devices
- Network traffic anomalies showing large HTTP request payloads directed at IP phone management interfaces
- Authentication bypass attempts or unauthorized configuration changes on IP phone systems
Detection Strategies
- Implement network intrusion detection rules to identify abnormally large HTTP requests targeting Cisco SPA IP phone IP addresses
- Monitor web server logs on IP phones for unusual request patterns, error codes, or access attempts
- Deploy network traffic analysis to detect exploitation attempts characterized by oversized HTTP payloads
- Use vulnerability scanners to identify exposed Cisco SPA IP phone management interfaces in your environment
Monitoring Recommendations
- Enable logging on network devices monitoring traffic to and from IP phone VLANs
- Configure SIEM alerts for HTTP traffic anomalies targeting known IP phone management interface addresses
- Implement periodic vulnerability assessments to identify unpatched or exposed IP phone devices
- Monitor for unexpected outbound connections from IP phone devices that may indicate compromise
How to Mitigate CVE-2024-20454
Immediate Actions Required
- Isolate Cisco SPA300 and SPA500 Series IP phones from untrusted networks and limit management interface access
- Implement network segmentation to prevent unauthorized access to IP phone management interfaces
- Disable web-based management interfaces where not operationally required
- Plan for device replacement as these products have reached end-of-life status
Patch Information
According to the Cisco Security Advisory, Cisco has not released and will not release firmware updates to address this vulnerability. The Cisco SPA300 Series and SPA500 Series IP phones have entered the end-of-life process, and Cisco has discontinued support for these devices.
Organizations using affected devices should plan migration to supported IP phone models that receive regular security updates. Cisco recommends reviewing end-of-life notices and transitioning to current-generation products.
Workarounds
- Restrict network access to IP phone management interfaces using access control lists (ACLs) or firewall rules
- Place IP phones on isolated VLANs with strict ingress/egress filtering
- Use VPN or jump hosts to access management interfaces only from trusted administrative workstations
- Disable HTTP/HTTPS management access if alternate management methods (such as provisioning servers) are available
# Example ACL to restrict management access (Cisco IOS syntax)
access-list 101 permit tcp 10.0.0.0 0.0.0.255 host 192.168.1.100 eq 80
access-list 101 permit tcp 10.0.0.0 0.0.0.255 host 192.168.1.100 eq 443
access-list 101 deny tcp any host 192.168.1.100 eq 80
access-list 101 deny tcp any host 192.168.1.100 eq 443
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
