CVE-2026-15789 in BuildKit
Summary
by MITRE • 07/21/2026
A custom client can produce such an upload request to the BuildKit daemon that files can escape from the BuildKit-controlled state directory. The client needs to have valid permissions to access the BuildKit control API to issue builds, e.g., bypass authentication, etc.
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Analysis
by VulDB Data Team • 07/21/2026
This vulnerability represents a critical privilege escalation and data exfiltration vector within container build environments that leverages improper access controls in the BuildKit daemon implementation. The flaw allows authenticated attackers with access to the BuildKit control API to manipulate upload requests in ways that enable file system traversal and escape from the controlled build environment state directory. This creates an arbitrary file read condition where malicious clients can potentially access files outside of their intended build context, undermining the fundamental security boundaries that containerized build processes are designed to maintain.
The technical implementation of this vulnerability stems from insufficient input validation and path sanitization within the BuildKit daemon's handling of file upload requests. When a client submits an upload request containing specially crafted file paths or traversal sequences, the daemon fails to properly validate these inputs against the expected build context boundaries. This weakness enables attackers to bypass the sandboxed environment constraints that typically isolate build operations from the underlying host filesystem. The vulnerability specifically manifests when the BuildKit daemon processes file paths without proper canonicalization or directory traversal prevention mechanisms, allowing maliciously formatted requests to reference files outside the designated state directory.
Operational impact of this vulnerability extends beyond simple data exposure to encompass potential system compromise and lateral movement within containerized environments. An attacker with valid BuildKit API access could exploit this flaw to read sensitive configuration files, credential stores, or other privileged information stored on the host system. The attack surface is particularly concerning in multi-tenant environments where multiple users share the same BuildKit daemon instance, as it could enable one user to access another's build artifacts or system resources. Additionally, this vulnerability undermines the security model of container build systems by breaking the isolation guarantees that are essential for secure software supply chain operations.
Mitigation strategies should focus on implementing robust input validation and path sanitization within the BuildKit daemon components, ensuring all file paths undergo proper canonicalization before processing. Organizations should enforce strict access controls and authentication mechanisms to limit who can interact with the BuildKit API, as the vulnerability requires valid API credentials to exploit. Implementing network segmentation and privilege separation between build systems and critical infrastructure can reduce the potential impact of successful exploitation. System administrators should also consider monitoring for unusual file access patterns or path traversal attempts within build environments, which could indicate exploitation attempts. This vulnerability aligns with CWE-22 Path Traversal and CWE-73 Improper Neutralization of Special Elements in Output Used by a Downstream Component, and corresponds to ATT&CK technique T1059 Command and Scripting Interpreter for executing malicious commands through compromised build environments. Regular security audits of container build systems and implementation of least privilege principles for BuildKit access should be prioritized to prevent unauthorized exploitation.