CVE-2026-4374: RTI Connext Professional XXE Vulnerability

CVE-2026-4374 Overview

CVE-2026-4374 is an XML External Entity (XXE) vulnerability affecting RTI Connext Professional services. This improper restriction of XML External Entity Reference vulnerability allows attackers to exploit serialized data external linking capabilities within critical RTI Connext Professional components including Routing Service, Observability Collector, Recording Service, Queueing Service, and Cloud Discovery Service. The vulnerability enables malicious actors to reference external entities within XML documents, potentially leading to sensitive data disclosure and service disruption.

Critical Impact

Network-accessible XXE vulnerability in RTI Connext Professional middleware services can lead to confidential data exfiltration and denial of service conditions across distributed systems infrastructure.

Affected Products

• RTI Connext Professional - Routing Service
• RTI Connext Professional - Observability Collector
• RTI Connext Professional - Recording Service
• RTI Connext Professional - Queueing Service
• RTI Connext Professional - Cloud Discovery Service

Discovery Timeline

• April 1, 2026 - CVE-2026-4374 published to NVD
• April 1, 2026 - Last updated in NVD database

Technical Details for CVE-2026-4374

Vulnerability Analysis

This vulnerability stems from improper restriction of XML External Entity (XXE) references (CWE-611) within the XML parsing functionality of RTI Connext Professional services. The affected components process XML configuration and data exchange documents without adequately restricting external entity declarations. When malicious XML documents containing external entity references are processed by vulnerable services, attackers can leverage this weakness for serialized data external linking attacks.

The network-accessible nature of these services significantly increases the risk, as no authentication is required and user interaction is not necessary for exploitation. The attack complexity is low, making this vulnerability particularly dangerous in enterprise environments where RTI Connext Professional middleware is deployed for real-time distributed systems communication.

Root Cause

The root cause lies in the XML parsing implementation within RTI Connext Professional services that fails to properly disable or restrict the processing of external entity declarations (DOCTYPE declarations with SYSTEM or PUBLIC identifiers). When XML parsers are configured to resolve external entities by default, attackers can craft malicious XML payloads that reference external resources, including local files or remote URLs, forcing the parser to fetch and include their contents.

Attack Vector

The vulnerability is exploitable over the network without authentication. An attacker can send specially crafted XML documents to any of the affected RTI Connext Professional services. These malicious documents contain external entity declarations that, when processed by the vulnerable XML parser, can:

1. Read sensitive files from the local file system and exfiltrate them to attacker-controlled servers
2. Perform Server-Side Request Forgery (SSRF) attacks against internal network resources
3. Cause denial of service through entity expansion attacks (XML bombs) or by referencing slow or non-responsive external resources

The exploitation process involves submitting an XML document with a DOCTYPE declaration defining an external entity pointing to a target resource, then referencing that entity within the document body to trigger retrieval and processing.

Detection Methods for CVE-2026-4374

Indicators of Compromise

• Unusual XML documents containing DOCTYPE declarations with SYSTEM or PUBLIC identifiers in service logs
• Unexpected outbound network connections from RTI Connext Professional services to external or internal resources
• Log entries showing file access attempts to sensitive system files such as /etc/passwd, /etc/shadow, or configuration files
• Error messages related to XML parsing failures referencing external URIs

Detection Strategies

• Monitor and alert on XML documents containing DOCTYPE declarations with external entity references in incoming traffic to RTI Connext Professional services
• Implement network-level monitoring for unexpected outbound connections from middleware services
• Deploy application-layer firewalls capable of inspecting and blocking malicious XML payloads
• Configure SIEM rules to detect patterns associated with XXE exploitation attempts

Monitoring Recommendations

• Enable verbose logging on all affected RTI Connext Professional services to capture XML processing activities
• Monitor network traffic for unusual DNS queries or HTTP requests originating from middleware service hosts
• Implement file integrity monitoring on systems hosting RTI Connext Professional services
• Establish baseline behavior for service network communications and alert on deviations

How to Mitigate CVE-2026-4374

Immediate Actions Required

• Review and apply patches or updates from RTI as documented in the RTI Vulnerability Advisory
• Restrict network access to affected RTI Connext Professional services using firewall rules and network segmentation
• Implement input validation at network perimeters to filter XML documents containing DOCTYPE declarations
• Monitor affected services for signs of exploitation while awaiting patch deployment

Patch Information

Organizations should consult the official RTI vulnerability advisory for specific patch information and remediation guidance. The advisory is available at the RTI Vulnerabilities page. Contact RTI support for access to patched versions of the affected Connext Professional components.

Workarounds

• Configure XML parsers within RTI Connext Professional services to disable external entity processing where configuration options are available
• Deploy Web Application Firewalls (WAF) or API gateways with XXE detection capabilities in front of exposed services
• Implement strict network segmentation to limit the blast radius of potential exploitation
• Use application-level whitelisting to restrict XML document structures accepted by services

# Example: Restricting network access to RTI Connext services using iptables
# Allow only trusted IP ranges to access Routing Service port
iptables -A INPUT -p tcp --dport 7400 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 7400 -j DROP

# Enable logging for blocked connection attempts
iptables -A INPUT -p tcp --dport 7400 -j LOG --log-prefix "RTI_ACCESS_BLOCKED: "