Buffer Overflow in Dnsmasq-utils dhcp_release Causes DoS

Executive Summary

Dnsmasq-utils version 2.79-1 contains a buffer overflow vulnerability in the dhcp_release utility. This vulnerability occurs because the program copies input into a fixed-size buffer without proper bounds checking. Specifically, if an attacker supplies an input string longer than 16 characters, it causes a buffer overflow.

This overflow can cause the dhcp_release process to crash and produce a core dump, effectively causing a denial of service.

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Impact Analysis

This vulnerability can be exploited by an attacker to cause a denial of service (DoS) on systems running the vulnerable dhcp_release utility. By sending a specially crafted input longer than 16 characters, the attacker can crash the dhcp_release process, potentially disrupting DHCP lease management.

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Compliance Impact

I don't know

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Detection Guidance

[{'type': 'paragraph', 'content': 'This vulnerability can be detected by testing the dhcp_release utility with input strings longer than 16 characters to see if it crashes or produces a core dump.'}, {'type': 'paragraph', 'content': "A practical detection method is to run the dhcp_release command with an argument consisting of a long string, such as a sequence of 'A' characters exceeding 16 in length."}, {'type': 'paragraph', 'content': 'For example, you can use the following command in a Linux shell to test the vulnerability:'}, {'type': 'list_item', 'content': 'python3 -c "import os; os.system(\'dhcp_release \' + \'A\'*20)"'}, {'type': 'paragraph', 'content': 'If the dhcp_release process aborts and generates a core dump, it indicates the presence of the buffer overflow vulnerability.'}] [2]

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Mitigation Strategies

To mitigate this vulnerability, avoid using the vulnerable dhcp_release utility with untrusted or excessively long input strings.

Immediate steps include:

• Restrict access to the dhcp_release utility to trusted users only.
• Monitor and filter inputs to dhcp_release to ensure they do not exceed 16 characters.
• Apply any available patches or updates from your distribution or the dnsmasq project that address this buffer overflow.

If no patch is available, consider disabling or replacing the dhcp_release utility until a fix is applied.

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