CVE-2025-55853: SoftVision webPDF SSRF Vulnerability

CVE-2025-55853 Overview

CVE-2025-55853 is a Server-Side Request Forgery (SSRF) vulnerability affecting SoftVision webPDF before version 10.0.2. The PDF converter function fails to properly validate whether internal or external resources are being requested in uploaded files, allowing potentially dangerous protocols such as http:// and file:///. This flaw enables attackers to upload malicious XML or HTML files that, when processed and rendered to PDF, can facilitate internal port scanning and Local File Inclusion (LFI) attacks against the server.

Critical Impact

Attackers can leverage this SSRF vulnerability to perform internal network reconnaissance through port scanning and read sensitive local files via LFI, potentially exposing confidential configuration data, credentials, and internal service information.

Affected Products

• SoftVision webPDF versions prior to 10.0.2
• webPDF PDF converter service with XML/HTML processing capabilities
• Systems exposing webPDF document conversion functionality

Discovery Timeline

• 2026-02-19 - CVE-2025-55853 published to NVD
• 2026-02-19 - Last updated in NVD database

Technical Details for CVE-2025-55853

Vulnerability Analysis

This Server-Side Request Forgery vulnerability exists in the PDF converter component of SoftVision webPDF. When the application processes uploaded XML or HTML files for conversion to PDF format, it fails to implement proper validation of external resource references embedded within those documents. The converter blindly follows URLs and file path references, including dangerous protocol handlers like http:// for network requests and file:/// for local file system access.

The lack of input validation on resource URIs creates a classic SSRF attack surface. An attacker can craft malicious documents containing specially constructed resource references that force the server to make requests to arbitrary destinations. When targeting internal network addresses, this enables reconnaissance of services running on internal hosts and ports that would otherwise be inaccessible from external networks.

Root Cause

The root cause of this vulnerability lies in insufficient input validation within the webPDF document converter's resource fetching mechanism. The application does not implement proper URL scheme whitelisting or destination address validation before fetching external resources during the PDF rendering process. This allows the processing of arbitrary protocol handlers and enables requests to internal network addresses and local file paths.

Attack Vector

The attack vector involves uploading a malicious XML or HTML document to the webPDF conversion service. The document contains crafted resource references (such as external stylesheets, images, or entity references) pointing to internal network addresses or local file paths. When webPDF processes the document for PDF conversion, it attempts to fetch these resources, effectively proxying attacker-controlled requests through the server.

For internal port scanning, an attacker can enumerate internal services by referencing various IP addresses and ports, observing response behavior differences to identify active services. For Local File Inclusion, using the file:/// protocol handler allows reading sensitive files such as /etc/passwd, configuration files, or application credentials that get embedded into the generated PDF output.

Technical details and proof-of-concept demonstrations are available in the GitHub PoC Repository. Additional information about the affected product can be found on the webPDF Service Overview page.

Detection Methods for CVE-2025-55853

Indicators of Compromise

• Unusual PDF conversion requests containing file:/// protocol references in uploaded XML or HTML documents
• Server-side network connections to internal IP ranges (e.g., 10.x.x.x, 172.16.x.x, 192.168.x.x) originating from the webPDF service
• PDF output files containing unexpected file content or internal service responses
• High volume of PDF conversion requests targeting various internal port combinations

Detection Strategies

• Monitor webPDF service logs for uploaded documents containing suspicious protocol handlers (file://, gopher://, dict://)
• Implement network intrusion detection rules to alert on internal network scanning patterns from web application servers
• Analyze generated PDF documents for embedded content that should not be accessible to external users
• Deploy web application firewall (WAF) rules to inspect uploaded XML/HTML content for SSRF payload patterns

Monitoring Recommendations

• Enable detailed logging on the webPDF conversion service to capture all resource fetch attempts
• Monitor network egress from webPDF servers for connections to internal network segments
• Implement file integrity monitoring on sensitive configuration files that may be targeted via LFI
• Set up alerts for unusual patterns in PDF file sizes that may indicate data exfiltration through embedded content

How to Mitigate CVE-2025-55853

Immediate Actions Required

• Upgrade SoftVision webPDF to version 10.0.2 or later immediately
• Restrict webPDF service network access to prevent connections to internal network ranges
• Review and audit recent PDF conversion logs for potential exploitation attempts
• Implement network segmentation to isolate the webPDF service from sensitive internal resources

Patch Information

SoftVision has addressed this vulnerability in webPDF version 10.0.2. Organizations should update to this version or later to remediate the SSRF vulnerability. The patch implements proper validation of resource URIs during document processing, restricting dangerous protocol handlers and preventing access to internal network resources.

For the latest security updates and patch information, consult the webPDF Service Overview page.

Workarounds

• Configure network-level controls to block outbound connections from the webPDF server to internal network ranges and localhost
• Disable or restrict support for XML and HTML file uploads if PDF conversion from these formats is not a business requirement
• Implement a strict allowlist of permitted external domains for resource fetching during document conversion
• Deploy the webPDF service in an isolated network segment with no access to internal services or sensitive file systems

# Example: Network-level mitigation using iptables to block internal network access
# Block webPDF service from accessing internal networks
iptables -A OUTPUT -m owner --uid-owner webpdf -d 10.0.0.0/8 -j DROP
iptables -A OUTPUT -m owner --uid-owner webpdf -d 172.16.0.0/12 -j DROP
iptables -A OUTPUT -m owner --uid-owner webpdf -d 192.168.0.0/16 -j DROP
iptables -A OUTPUT -m owner --uid-owner webpdf -d 127.0.0.0/8 -j DROP