CVE-2025-21379 has been identified as a critical DHCP client service remote code execution vulnerability. If exploited successfully, this vulnerability can allow an attacker to execute arbitrary code on targeted systems running vulnerable versions of the DHCP client service. This article provides an in-depth analysis of the vulnerability, delving into its mechanics, potential exploit scenarios, and how it can be mitigated. Additionally, we'll look at some code snippets and point you to original references for a deeper understanding.

Background

The Dynamic Host Configuration Protocol (DHCP) is a widely used network protocol that dynamically assigns IP addresses and other network configuration information to network devices. DHCP plays a crucial role in managing and distributing network resources, making it an ideal target for threat actors to exploit.

CVE-2025-21379 affects the DHCP client service, a core component that handles the parsing and processing of DHCP messages. Due to a coding error in the parsing process, malicious DHCP server responses can trigger a buffer overflow leading to remote code execution (RCE) on affected systems.

Technical Analysis

The root cause of the vulnerability resides in the improper handling of DHCP options during the processing of the DHCP server response. Here's a code snippet that demonstrates the issue:

void process_dhcp_options(void* response_data, int len) {
    for (int i = ; i < len; i++) {
        char optionID = response_data[i];
        char optionLen = response_data[i + 1];

        // ... processing options ...

        i += (optionLen - 1); 
    }
}

In the above code, the 'optionLen' value is directly extracted from the received DHCP response data without proper validation. This can result in a mismatch between the actual and expected lengths of the options, causing the loop to iterate beyond the bounds of the response_data buffer. Consequently, an out-of-bounds read error occurs, potentially leading to a buffer overflow and RCE.

Exploit Details

To exploit this vulnerability, an attacker typically sets up a rogue DHCP server on the targeted network, configured to send malicious DHCP server responses containing crafted DHCP options. When a vulnerable client sends a DHCP request, the rogue server sends back a malformed response containing a crafted payload designed to trigger the RCE vulnerability. The process can be summarized as follows:

For more detailed information on exploiting this vulnerability, check out the following resources

- Original Advisory
- Exploit-DB

To protect yourself from this vulnerability

1. Ensure you are running the latest version of the affected software, which contains a patch that fixes this vulnerability.

Configure host-based firewalls to limit incoming traffic to trusted sources.

3. Consider implementing DHCP snooping on your network switches to prevent rogue DHCP servers from operating.

Stay vigilant and make sure your systems are always up to date. Following best security practices, such as implementing security awareness training and conducting regular vulnerability assessments, will go a long way in keeping your infrastructure secure.

Conclusion

CVE-2025-21379 is an important vulnerability that needs to be addressed quickly to prevent unauthorized RCE on affected systems. As with any security issue, understanding the underlying mechanics of the vulnerability and keeping yourself informed about the latest trends in the threat landscape is essential. Stay safe, stay secure.

Timeline

Published on: 02/11/2025 18:15:36 UTC
Last modified on: 03/12/2025 01:42:13 UTC