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What is a Heap-Based Buffer Overflow Vulnerability?
1/24/2024 - Brian O'Neill

If a Heap-Based Buffer Overflow vulnerability is present in one of our image parsing or rendering technologies, threat actors can potentially exploit the vulnerability to run arbitrary code on our servers, and they can even crash our systems to cause Distributed Denial of Service (DDoS). This attack vector doesn't require any malware - making traditional antivirus software irrelevant as a defense method - and its outcomes can be just as devastating as any virus- or malware-based attack.

memory graphic

To understand what a heap-based buffer overflow vulnerability is, we first need to understand how heap memory works and exactly what buffers are.

What is Heap Memory?

The heap is a specific portion of a computer’s memory which is set aside for allocation. Our applications need a certain amount of memory to process incoming data, and modern-day systems tend to allocate finite amounts of these available memory segments dynamically. Application developers can also be directly responsible for the allocation or deallocation of heap memory.

What is a Buffer?

A buffer is a block of memory designed to hold and store data temporarily. It sees use across a variety of unique operations within a software program, such as reading or writing data. As data flows between different components or processes in an application, the buffer effectively helps manage the flow of that data.

How does a Heap-Based Buffer Overflow Occur?

Because heap memory is a finite resource, inputs that are too large can overrun a heap memory buffer and begin bleeding into adjacent memory allocations. This happens when input data (i.e., an image file upload) isn’t properly validated to ensure it rigorously conforms with the limitations of the application’s heap memory allocation.

How do Threat Actors Exploit Heap-Based Buffer Overflow Vulnerabilities?

When an image processing application is vulnerable to heap-based buffer overflow, an attacker can craft a malicious image file that intentionally exceeds the boundaries of a heap memory buffer, and they can subsequently impact what happens when that data spills over into adjacent memory allocations.

They can, for example, overwrite metadata living in adjacent memory, leading the application to execute the attacker’s code from a remote location (such as a specially crafted HTML page). They can also cause such a severe memory overflow that the application simply crashes, ensuring users are denied access to the service (resulting in a Denial-of-Service attack).

How can Heap-Based Buffer Overflow Vulnerabilities be Mitigated?

As with most software vulnerabilities, the onus of resolving specific security issues with an application or subset of related technologies (i.e., rendering & processing libraries) falls upon the application developers & their affiliated security teams. They need to use secure coding practices to ensure proper input validation, proper bounds checking, and safer memory functions.

Preventing Heap-Based Buffer Overflow Attacks with Cloudmersive

By deploying the Cloudmersive Advanced Virus Scan API ahead of our chosen suite of image processing applications, we can lean on powerful, independent content verification policies to ensure image files are thoroughly validated before they reach potentially vulnerable image processing applications. We can set custom request parameters to block invalid files, identify scripts and links within files, and much more.

Additionally, we can restrict incoming file types to a specific set of file extensions, limiting our attack surface by reducing the number of possible file types that any users can upload to our applications.

For more information on the Cloudmersive Advanced Virus Scan API, please do not hesitate to reach out to a member of our sales team.

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