> For the complete documentation index, see [llms.txt](https://alham-rizvi.gitbook.io/alhamrizvi/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://alham-rizvi.gitbook.io/alhamrizvi/binary-exp/03.-integer-overflow-md/challenge/medium/solution.md). # solution image This challenge demonstrates a **heap overflow caused by integer overflow in size calculation**. The program allocates memory for a shipment using `count * item_size`, but both variables are `unsigned short` (16-bit). This means the multiplication is also performed in 16-bit space, causing it to wrap around when the result exceeds 65535. By supplying values like `256` for both fields, the multiplication results in `65536`, which overflows to `0`. As a result, the program allocates a buffer of size 0 (handled as 1 byte internally), while logically treating it as a valid allocation. This mismatch between expected and actual allocation size is the core vulnerability. In real-world scenarios, this would allow an attacker to write beyond the allocated buffer and corrupt adjacent heap memory. In this challenge, the condition `allocated == 0` simulates successful exploitation and triggers the flag leak. This highlights how integer overflows in memory size calculations can lead to under-allocation and ultimately heap-based vulnerabilities. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://alham-rizvi.gitbook.io/alhamrizvi/binary-exp/03.-integer-overflow-md/challenge/medium/solution.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.