Vulnerable Open Source Dependencies: Counting Those That Matter.

Background: Vulnerable dependencies are a known problem in today's open-source software ecosystems because OSS libraries are highly interconnected and developers do not always update their dependencies. Aim: Our paper addresses the over-inflation problem of academic and industrial approaches for reporting vulnerable dependencies in OSS software, and therefore, caters to the needs of industrial practice for correct allocation of development and audit resources. Method: Careful analysis of deployed dependencies, aggregation of dependencies by their projects, and distinction of halted dependencies allow us to obtain a counting method that avoids over-inflation. To understand the industrial impact of a more precise approach, we considered the 200 most popular OSS Java libraries used by SAP in its own software. Our analysis included 10905 distinct GAVs (group, artifact, version) in Maven when considering all the library versions. Results: We found that about 20% of the dependencies affected by a known vulnerability are not deployed, and therefore, they do not represent a danger to the analyzed library because they cannot be exploited in practice. Developers of the analyzed libraries are able to fix (and actually responsible for) 82% of the deployed vulnerable dependencies. The vast majority (81%) of vulnerable dependencies may be fixed by simply updating to a new version, while 1% of the vulnerable dependencies in our sample are halted, and therefore, potentially require a costly mitigation strategy. Conclusions: Our case study shows that the correct counting allows software development companies to receive actionable information about their library dependencies, and therefore, correctly allocate costly development and audit resources, which is spent inefficiently in case of distorted measurements.