CVE-2021-3602 in Buildah
Summary
by MITRE • 03/03/2022
An information disclosure flaw was found in Buildah, when building containers using chroot isolation. Running processes in container builds (e.g. Dockerfile RUN commands) can access environment variables from parent and grandparent processes. When run in a container in a CI/CD environment, environment variables may include sensitive information that was shared with the container in order to be used only by Buildah itself (e.g. container registry credentials).
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 03/06/2022
The vulnerability identified as CVE-2021-3602 represents a critical information disclosure flaw within the Buildah container building tool that operates under chroot isolation mechanisms. This security weakness stems from inadequate process isolation during container image construction, specifically affecting how environment variables are handled across process hierarchies. The flaw manifests when Buildah executes container builds using chroot isolation, creating a scenario where child processes inherit environment variables from their parent and grandparent processes, thereby exposing sensitive data that should remain isolated.
This vulnerability operates at the intersection of process management and container security, leveraging the fundamental principle that processes spawned within chroot environments should maintain proper isolation boundaries. The technical implementation flaw occurs in how Buildah manages environment variable inheritance during the execution of Dockerfile RUN commands, where the isolation mechanisms fail to properly sanitize the environment variable space. This allows processes executing within container builds to access environment variables that were intended for the build process itself, potentially exposing credentials, tokens, and other sensitive information that may have been passed to the container for legitimate operational purposes.
The operational impact of CVE-2021-3602 is particularly severe in continuous integration and continuous deployment environments where Buildah is commonly employed. In such contexts, the vulnerability creates a direct pathway for credential leakage where sensitive information such as container registry credentials, API tokens, and access keys can be inadvertently exposed to processes running within container builds. This represents a significant risk to organizations relying on automated build pipelines, as the exposure can occur without explicit user interaction or awareness, potentially leading to unauthorized access to container registries, cloud resources, and other sensitive systems. The vulnerability essentially undermines the security assumptions of container isolation, creating a potential attack vector for adversaries seeking to harvest credentials from CI/CD pipelines.
The flaw aligns with CWE-200 (Information Disclosure) and demonstrates characteristics consistent with ATT&CK technique T1552.001 (Credentials In Files) and T1552.004 (Credentials in Secrets Management Stores), as it enables unauthorized access to sensitive information through process inheritance mechanisms. Organizations utilizing Buildah in their container build processes face significant risk of credential exposure, particularly in environments where automated builds frequently access external systems. The vulnerability can be exploited by malicious actors who gain access to build artifacts or who can influence the build process to capture environment variable contents from running processes. Mitigation strategies should focus on implementing proper environment variable sanitization, upgrading to patched versions of Buildah, and employing additional isolation mechanisms beyond chroot to prevent cross-process information leakage. Security teams should also consider implementing monitoring for unusual environment variable access patterns and establishing strict policies for credential handling in CI/CD environments to prevent accidental exposure through similar vulnerabilities.