CVE-2025-22873: os.Root Path Traversal Vulnerability

CVE-2025-22873 Overview

A path traversal vulnerability exists in the Go programming language's os.Root functionality that allows improper access to the parent directory. By opening a filename ending in ../, such as Root.Open("../"), an attacker can escape the intended root directory and access its parent. While this escape is limited to opening the parent directory itself and does not permit access to ancestors of the parent or files contained within it, the vulnerability still represents a breach of the intended directory isolation.

Critical Impact

Applications using Go's os.Root for directory sandboxing may be vulnerable to limited path traversal, potentially exposing the parent directory structure and contents to unauthorized access.

Affected Products

• Go programming language (versions utilizing vulnerable os.Root implementation)
• Applications built with affected Go versions that rely on os.Root for directory isolation

Discovery Timeline

• 2026-02-04 - CVE CVE-2025-22873 published to NVD
• 2026-02-05 - Last updated in NVD database

Technical Details for CVE-2025-22873

Vulnerability Analysis

This vulnerability is classified as CWE-23 (Relative Path Traversal). The flaw resides in how Go's os.Root type handles filenames that end with the path traversal sequence ../. The os.Root type is designed to provide a restricted view of the filesystem, confining file operations to a specific directory tree. However, the implementation fails to properly validate and sanitize path components when the traversal sequence appears at the end of the filename string.

The vulnerability requires local access to exploit, meaning an attacker needs some level of access to the system or application to leverage this flaw. While the scope is limited—only the immediate parent directory can be accessed, not further ancestors or files within—this still undermines the security guarantees that os.Root is meant to provide.

Root Cause

The root cause stems from improper input validation in the path handling logic of os.Root.Open(). When processing filenames, the function does not adequately handle edge cases where the path traversal sequence ../ appears as a trailing component. This allows the path resolution to escape the intended root boundary and resolve to the parent directory. The validation logic likely normalizes paths but fails to account for this specific pattern, treating the trailing ../ as a valid directory reference rather than rejecting it as an attempted escape.

Attack Vector

The attack vector is local, requiring the attacker to have the ability to influence the filename parameter passed to Root.Open() or similar functions. In a typical attack scenario:

1. An application uses os.Root to create a sandboxed directory environment
2. User-controlled input is used to construct file paths within this sandbox
3. The attacker provides a path ending in ../ (e.g., `"../")
4. The Root.Open() function processes this path and opens the parent directory instead of rejecting the traversal attempt
5. The attacker gains read access to the parent directory's contents

The vulnerability mechanism involves crafting a path string that terminates with the ../ sequence. When Root.Open("../") is called, instead of returning an error or confining the operation to the root directory, the function successfully opens the parent directory of the designated root. For detailed technical information, refer to the Go.dev Issue Tracker Entry and the Go.dev Vulnerability Report.

Detection Methods for CVE-2025-22873

Indicators of Compromise

• Application logs showing file access patterns with paths ending in ../
• Unexpected directory listing operations targeting parent directories of sandboxed roots
• Error logs indicating access attempts outside expected directory boundaries

Detection Strategies

• Review application code for usage of os.Root.Open() with user-controlled input
• Implement logging and monitoring for path traversal patterns in file operations
• Audit Go application dependencies to identify vulnerable Go runtime versions
• Use static analysis tools to detect potential path traversal vulnerabilities in Go code

Monitoring Recommendations

• Enable verbose logging for file system operations in Go applications using os.Root
• Monitor for unusual directory access patterns, particularly parent directory traversal attempts
• Implement alerting for any file operations that resolve outside the intended root directory
• Review audit logs for patterns indicating exploitation attempts

How to Mitigate CVE-2025-22873

Immediate Actions Required

• Update to a patched version of Go that addresses this vulnerability
• Review and audit all code paths where user input influences os.Root.Open() parameters
• Implement additional input validation to reject paths containing or ending with ../ sequences
• Consider implementing defense-in-depth measures such as chroot jails or containerization

Patch Information

The Go development team has addressed this vulnerability in a patch. For specific patch details, refer to the Go.dev Update Notice. The fix ensures proper handling of path traversal sequences when they appear at the end of filenames, preventing the escape from the designated root directory.

For comprehensive information about this vulnerability and the official fix, see the Golang Announcement Post and the Openwall OSS Security Discussion.

Workarounds

• Implement application-level path validation that strips or rejects any path containing ../ sequences before passing to os.Root functions
• Use additional sandboxing mechanisms such as containers or OS-level filesystem restrictions to limit potential impact
• Validate and sanitize all user-provided file paths using strict allowlist patterns that explicitly define permitted characters and path structures
• Consider using absolute path resolution and validation before any os.Root operations

# Example: Input validation pattern for Go applications
# Reject any paths containing traversal sequences before using os.Root
# Ensure paths do not end with ../ or contain /../ patterns
# Apply strict path normalization and validation in application code