MRuby VM Escape – step by step

Last post we discussed format string implementation vulnerabilities, and focused on the vulnerabilities in the (C/M)Ruby implementation. Since shopify integrated MRuby in a VM-like scenario, we will present a step-by-step exploitation of the main shown vulnerability, achieving a VM escape.

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Format Strings – Behind the Scenes

Format string vulnerabilities belong to a special family of vulnerabilities: a family of vulnerabilities that were once destructive but now days receive a decreasing amount of attention. Since most vulnerable code samples are based on poor C/C++ programming education, much like SQL Injections in SQL, most researchers believe that this vulnerability group can be completely mitigated with proper coding standards. However, this blog post will address a hidden aspect of the format string vulnerability, one that can impact quite a large number of high level programming languages.

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