CVE-2026-5258: IOPaint Path Traversal Vulnerability

CVE-2026-5258 Overview

A path traversal vulnerability has been identified in Sanster IOPaint version 1.5.3, specifically within the _get_file function located in the iopaint/file_manager/file_manager.py component. This vulnerability allows remote attackers to manipulate the filename argument to traverse directory paths, potentially accessing files outside the intended directory structure. The exploit has been publicly disclosed, and despite early contact attempts, the vendor has not responded to the disclosure.

Critical Impact

Remote attackers can exploit this path traversal vulnerability to read arbitrary files on the system, potentially exposing sensitive configuration files, credentials, or application source code.

Affected Products

• Sanster IOPaint 1.5.3
• IOPaint File Manager Component (iopaint/file_manager/file_manager.py)

Discovery Timeline

• 2026-04-01 - CVE-2026-5258 published to NVD
• 2026-04-01 - Last updated in NVD database

Technical Details for CVE-2026-5258

Vulnerability Analysis

This path traversal vulnerability (CWE-22) exists in the IOPaint File Manager component, which is used for handling file operations within the image processing application. The vulnerable _get_file function fails to properly sanitize the filename parameter before using it in file system operations. This allows attackers to craft malicious requests containing directory traversal sequences such as ../ to escape the intended directory context and access files elsewhere on the system.

The vulnerability is remotely exploitable without requiring authentication, making it accessible to any attacker who can reach the IOPaint service over the network. The impact includes potential unauthorized read access to sensitive files on the affected system.

Root Cause

The root cause of this vulnerability is improper input validation in the _get_file function within file_manager.py. The function accepts a user-supplied filename parameter without adequately sanitizing or validating it against path traversal sequences. This allows attackers to include relative path components (e.g., ../) in the filename, enabling traversal outside the intended file directory.

Proper mitigation would require implementing strict input validation, canonicalizing file paths, and ensuring the resolved path remains within the allowed directory boundaries before performing any file operations.

Attack Vector

The attack can be executed remotely over the network. An attacker sends a crafted HTTP request to the IOPaint service with a manipulated filename parameter containing path traversal sequences. By including sequences like ../../../etc/passwd, the attacker can traverse out of the application's designated file directory and access arbitrary files readable by the application process.

The vulnerability does not require any authentication or special privileges, and can be exploited without user interaction. The attack complexity is low, making this vulnerability accessible to attackers with minimal technical sophistication.

For detailed technical information about this vulnerability, see the GitHub Issue Discussion and VulDB Entry #354448.

Detection Methods for CVE-2026-5258

Indicators of Compromise

• HTTP requests to IOPaint endpoints containing path traversal sequences such as ../, ..%2f, or ..%5c in filename parameters
• Unusual file access patterns in application logs indicating attempts to read files outside expected directories
• Web server access logs showing requests with encoded traversal patterns targeting the File Manager component
• Error messages or responses indicating access to system files like /etc/passwd or configuration files

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block requests containing path traversal patterns
• Monitor application logs for file access attempts targeting paths outside the designated upload/file directories
• Deploy network intrusion detection signatures to identify path traversal exploitation attempts in HTTP traffic
• Enable verbose logging in the IOPaint application to capture all file access requests for forensic analysis

Monitoring Recommendations

• Configure alerts for any file access requests containing ../ sequences or URL-encoded equivalents
• Monitor for abnormal response sizes that might indicate successful extraction of sensitive files
• Implement file integrity monitoring on critical system files that could be targeted through path traversal
• Review IOPaint access logs regularly for patterns indicating reconnaissance or exploitation attempts

How to Mitigate CVE-2026-5258

Immediate Actions Required

• Restrict network access to the IOPaint service to trusted networks or users only
• Implement a web application firewall (WAF) rule to block requests containing path traversal sequences
• Consider disabling the File Manager component if it is not critical to operations
• Review and audit any files that may have been accessed through this vulnerability

Patch Information

At the time of publication, no official patch has been released by the vendor. The vendor was contacted regarding this disclosure but did not respond. Users should monitor the VulDB Entry and the official IOPaint repository for any future security updates.

Workarounds

• Deploy a reverse proxy with input validation rules to sanitize incoming requests before they reach IOPaint
• Implement filesystem-level permissions to restrict the IOPaint process to only necessary directories
• Use containerization or sandboxing to isolate the IOPaint application and limit the impact of path traversal exploitation
• Configure the web server to reject requests with path traversal patterns at the ingress point

# Example nginx configuration to block path traversal attempts
location /iopaint/ {
    # Block requests containing path traversal sequences
    if ($request_uri ~* "\.\.") {
        return 403;
    }
    
    # Additional URL-encoded traversal pattern blocking
    if ($request_uri ~* "%2e%2e") {
        return 403;
    }
    
    proxy_pass http://localhost:8080;
}