CVE-2026-39822 in Go standard library
Summary
by MITRE • 07/08/2026
On Unix systems, opening a file in an os.Root improperly follows symlinks to locations outside of the Root when the final path component of the a path is a symbolic link and the path ends in /. For example, 'root.Open("symlink/")' will open "symlink" even when "symlink" is a symbolic link pointing outside of the root.
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Analysis
by VulDB Data Team • 07/08/2026
This vulnerability represents a critical path traversal issue that fundamentally undermines the security boundaries established by chroot environments and container isolation mechanisms. The flaw occurs specifically within the os.Root package implementation on unix systems where file operations fail to properly enforce directory restrictions when dealing with symbolic links that terminate with trailing slashes. When a caller invokes root.Open("symlink/") with a path ending in a forward slash, the system incorrectly follows the symbolic link to its target location regardless of whether that target resides outside the designated root directory. This behavior directly violates the fundamental principle of chroot isolation which is designed to contain processes within a specific directory tree and prevent access to arbitrary system resources.
The technical implementation of this vulnerability stems from improper path resolution logic that does not account for the special handling required when symbolic links are present at the final component of a path. In unix filesystems, the trailing slash in a path component indicates that the system should treat the component as a directory reference rather than a file reference, but the vulnerable implementation fails to maintain the root boundary constraints during this resolution process. The flaw is particularly insidious because it allows attackers to bypass directory restrictions through carefully crafted symbolic link chains that can lead to information disclosure, privilege escalation, or denial of service attacks. This issue aligns with CWE-22 Path Traversal vulnerabilities and specifically manifests as a weakness in access control enforcement mechanisms.
The operational impact of this vulnerability extends far beyond simple path resolution errors and can severely compromise the security posture of any system relying on chroot isolation for process containment. Attackers can exploit this flaw to access files and directories outside of the intended root environment, potentially gaining access to sensitive system information, configuration files, or even other running processes. The vulnerability affects applications that utilize os.Root functionality for containerized environments, virtual machines, or any security context where directory boundaries must be maintained. This weakness directly enables techniques described in the MITRE ATT&CK framework under T1565.001 Credential Access: Steal or forge credentials, as well as T1078 Valid Accounts, by allowing unauthorized access to system resources that should remain isolated. The impact is particularly severe in cloud environments and container orchestration platforms where proper isolation boundaries are critical for multi-tenant security.
Mitigation strategies for this vulnerability must address both the immediate implementation flaw and broader architectural considerations for secure path handling. System administrators should immediately patch affected implementations of os.Root functionality to ensure that symbolic links terminating with trailing slashes properly respect root directory boundaries. The fix requires implementing strict enforcement of directory boundary checks during path resolution, particularly when the final component of a path is a symbolic link. Organizations should also implement comprehensive monitoring for suspicious file access patterns that might indicate exploitation attempts. Additionally, security teams should review all applications utilizing chroot or similar isolation mechanisms to ensure they properly validate path components and enforce access controls at every level of the filesystem hierarchy. The solution aligns with security best practices outlined in NIST SP 800-125 for container security and emphasizes the critical importance of proper input validation and access control enforcement in preventing privilege escalation attacks.