Source: psirt@esri.com
ArcGIS Server versions 11.5 and earlier on Windows and Linux do not sufficiently validate uploaded files, enabling a remote unauthenticated attacker to upload arbitrary files to the server’s designated upload directories. However, the server’s architecture enforces controls that restrict uploaded files to non‑executable storage locations and prevent modification or replacement of existing application components or system configurations. Uploaded files cannot be executed, leveraged to escalate privileges, or used to access sensitive data. Because the issue does not enable execution, service disruption, unauthorized access, or integrity compromise, its impact on confidentiality, integrity, and availability is low. Note that race conditions, secret values, or man‑in‑the‑middle conditions are required for exploitation.
ArcGIS Server versions 11.5 and earlier are vulnerable to arbitrary file upload, allowing attackers to place files on the server. While the vulnerability does not directly lead to remote code execution (RCE) or data compromise due to architectural restrictions, it could be leveraged in conjunction with other vulnerabilities or to facilitate future attacks. Exploitation requires specific conditions like race conditions or man-in-the-middle scenarios to achieve any meaningful impact.
Step 1: Identify Upload Endpoint: The attacker identifies the specific endpoint within ArcGIS Server that handles file uploads. This might be a documented API, a web form, or a specific URL pattern.
Step 2: Craft Malicious File: The attacker crafts a malicious file, potentially containing a payload designed to exploit a future vulnerability or to be used in a later stage of an attack. The file type and content are chosen to bypass any initial validation checks.
Step 3: Upload the File: The attacker uploads the crafted file to the identified endpoint. The upload process bypasses the insufficient validation.
Step 4: File Placement: The server places the uploaded file in a designated directory. Due to architectural restrictions, this directory is non-executable.
Step 5: Post-Exploitation (Conditional): The attacker attempts to leverage the uploaded file. This could involve using it in conjunction with other vulnerabilities (e.g., a path traversal vulnerability) or attempting to exploit a race condition to overwrite a critical file. The success of this step depends on the presence of other vulnerabilities or specific server configurations.
The vulnerability stems from insufficient input validation on the server-side file upload functionality. Specifically, the ArcGIS Server fails to adequately sanitize or validate uploaded files, allowing an attacker to upload files to a designated directory. The root cause is likely a missing or incomplete check on file types, extensions, or content, permitting the upload of arbitrary files. However, the server's architecture mitigates the impact by restricting uploaded files to non-executable storage locations, preventing direct execution or modification of critical system components. The lack of direct RCE indicates the vulnerability lies in a logic flaw related to file upload validation, rather than a more severe vulnerability like a buffer overflow or memory corruption.
Due to the limited impact, this vulnerability is unlikely to be targeted by sophisticated APTs directly. However, it could be used as a stepping stone in a multi-stage attack. Not listed on CISA KEV.
Network traffic analysis: Monitor for unusual file upload activity to ArcGIS Server endpoints, especially uploads of unexpected file types or sizes.
File system monitoring: Regularly scan the designated upload directories for suspicious files or unexpected file modifications.
Web server logs: Analyze web server logs for POST requests to file upload endpoints, looking for unusual patterns or file names.
Intrusion Detection/Prevention Systems (IDS/IPS): Configure IDS/IPS rules to detect suspicious file upload attempts based on file types, sizes, and request patterns.
Upgrade to ArcGIS Server version 11.6 or later to patch the vulnerability.
Implement robust input validation on all file upload endpoints. This should include checks on file type, file extension, file size, and content.
Restrict file upload directories to only allow necessary file types.
Implement file scanning with antivirus software or a content-based file analysis tool to detect malicious content.
Regularly review and audit file upload configurations and access controls.
Implement a Web Application Firewall (WAF) to filter malicious requests.
Consider using a Content Delivery Network (CDN) to host static content and reduce the attack surface.