INVESTIGATING ESCAPE VULNERABILITIES IN CONTAINER RUNTIMES
thesisposted on 14.05.2021, 15:46 by Michael J Reeves
Container adoption has exploded in recent years with over 92% of companies using containers as part of their cloud infrastructure. This explosion is partly due to the easy orchestration and lightweight operations of containers compared to traditional virtual machines. As container adoption increases, servers hosting containers become more attractive targets for adversaries looking to gain control of a container to steal trade secrets, exfiltrate customer data, or hijack hardware for cryptocurrency mining. To control a container host, an adversary can exploit a vulnerability that enables them to escape from the container onto the host. This kind of attack is termed a “container escape” because the adversary is able to execute code on the host from within the isolated container. The vulnerabilities which allow container escape exploits originate from three main sources: (1) container profile misconfiguration, (2) the host’s Linux kernel, and (3) the container runtime. While the first two cases have been studied in the literature, to the best of the author’s knowledge, there is, at present, no work that investigates the impact of container runtime vulnerabilities. To fill this gap, a survey over container runtime vulnerabilities was conducted investigating 59 CVEs for 11 different container runtimes. As CVE data alone would limit the investigation analysis, the investigation focused on the 28 CVEs with publicly available proof of concept (PoC) exploits. To facilitate this analysis, each exploit was broken down into a series of high-level commands executed by the adversary called “steps”. Using the steps of each CVE’s corresponding exploit, a seven-class taxonomy of these 28 vulnerabilities was constructed revealing that 46% of the CVEs had a PoC exploit which enabled a container escape. Since container escapes were the most frequently occurring category, the nine corresponding PoC exploits were further analyzed to reveal that the underlying cause of these container escapes was a host component leaking into the container. This survey provides new insight into system vulnerabilities exposed by container runtimes thereby informing the direction of future research.