CVE-2017-10600 in ubuntu-image
Summary
by MITRE
ubuntu-image 1.0 before 2017-07-07, when invoked as non-root, creates files in the resulting image with the uid of the invoking user. When the resulting image is booted, a local attacker with the same uid as the image creator has unintended access to cloud-init and snapd directories.
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Analysis
by VulDB Data Team • 10/24/2019
The vulnerability identified as CVE-2017-10600 affects the ubuntu-image tool version 1.0 and earlier releases, specifically when executed by non-root users. This issue represents a significant privilege escalation concern within container and image creation environments where user identity preservation during image generation creates unintended access vectors for local attackers. The vulnerability stems from the tool's failure to properly sanitize file ownership when creating images, leading to persistent security risks that extend beyond the immediate execution context. The flaw operates under the principle of least privilege violation, where the tool maintains user identity rather than properly mapping to root or system-level ownership during image construction.
The technical implementation of this vulnerability involves the ubuntu-image utility's handling of file system metadata during image creation processes. When invoked by a non-root user, the tool preserves the invoking user's uid in the generated image files, creating a scenario where the image maintains the same user context as the creator. This behavior creates a persistent security boundary issue since the image, when booted, operates with the same user privileges as the creator. The vulnerability specifically affects cloud-init and snapd directories which are critical system components that require elevated privileges for proper operation. These directories contain sensitive configuration data, system management interfaces, and package management components that could be exploited by an attacker with matching uid privileges.
The operational impact of this vulnerability extends beyond simple file access and represents a comprehensive local privilege escalation vector. An attacker who can predict or match the uid of the image creator gains unauthorized access to system configuration data, package management interfaces, and cloud initialization processes that should remain restricted to system administrators. This creates a persistent backdoor within the image that can be exploited even after the initial creation process, as the image retains the original user context during execution. The vulnerability affects cloud environments, virtual machines, and containerized applications where ubuntu-image is used for system deployment, potentially allowing attackers to modify system configurations, access sensitive data, or manipulate package installations through the compromised directories.
Mitigation strategies for this vulnerability require immediate patching of the ubuntu-image tool to version 2017-07-07 or later, which addresses the uid preservation issue during image creation. System administrators should implement strict access controls on image creation environments to prevent unauthorized users from creating system images, particularly in multi-user environments where uid conflicts may occur. The remediation process should include verification that all existing images are re-created with patched versions of the tool, and that any images containing the vulnerable uid preservation behavior are deprecated. Security monitoring should be enhanced to detect unauthorized image creation activities, particularly in environments where cloud-init and snapd configurations are critical. Organizations should also consider implementing automated image validation processes that check for proper uid mapping and ownership during image construction to prevent similar issues in future deployments.
This vulnerability aligns with CWE-276, which addresses improper privileges, and represents a classic case of insufficient privilege separation in system tools. The ATT&CK framework categorizes this under privilege escalation techniques, specifically targeting local privilege escalation through improper file permissions and user context preservation. The issue demonstrates how seemingly benign tool behaviors can create persistent security risks when operating in environments where user identity mapping is not properly handled during system image creation processes. The vulnerability underscores the importance of proper privilege management and access control in system deployment tools, particularly those operating in cloud and containerized environments where image integrity is critical for overall system security.