CVE-2017-9458 in PAN-OS
Summary
by MITRE
XML external entity (XXE) vulnerability in the GlobalProtect internal and external gateway interface in Palo Alto Networks PAN-OS before 6.1.18, 7.0.x before 7.0.17, 7.1.x before 7.1.12, and 8.0.x before 8.0.3 allows remote attackers to obtain sensitive information, cause a denial of service, or conduct server-side request forgery (SSRF) attacks via unspecified vectors.
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Analysis
by VulDB Data Team • 01/10/2021
The CVE-2017-9458 vulnerability represents a critical XML external entity processing flaw within Palo Alto Networks PAN-OS firewalls that affects multiple version ranges including 6.1.17 and earlier, 7.0.16 and earlier, 7.1.11 and earlier, and 8.0.2 and earlier. This vulnerability specifically targets the GlobalProtect internal and external gateway interface components, which are essential for secure remote access and network protection services. The flaw stems from insufficient input validation and sanitization of XML data processed by the firewall's GlobalProtect service, creating a pathway for malicious actors to exploit the system through malformed XML requests. The vulnerability is classified under CWE-611 as an improper restriction of XML external entity reference, which directly enables attackers to manipulate how XML parsers handle external references and entities within the system. This weakness allows adversaries to leverage the XML processing capabilities of the firewall to access internal resources, retrieve sensitive data, and potentially compromise the entire network infrastructure.
The technical exploitation of this XXE vulnerability enables attackers to perform multiple malicious activities through server-side request forgery attacks that bypass traditional network security controls. Remote attackers can craft specially formatted XML requests that trigger the firewall's XML parser to resolve external entities, potentially accessing internal network resources, file systems, or even other network services that would normally be protected by the firewall's security policies. The vulnerability can result in information disclosure where sensitive data such as user credentials, system configurations, or internal network structures can be exfiltrated through carefully constructed entity references. Additionally, the flaw can be leveraged to cause denial of service conditions by exhausting system resources through recursive entity references or by forcing the firewall to make unauthorized network requests to external malicious servers. The server-side request forgery component allows attackers to use the firewall as a proxy to access internal systems that are otherwise unreachable from the external network, effectively bypassing network segmentation and access controls.
The operational impact of CVE-2017-9458 extends beyond simple data theft or service disruption to represent a fundamental compromise of network security posture for affected organizations. Organizations using vulnerable PAN-OS versions face the risk of unauthorized access to their internal networks through the GlobalProtect gateway interfaces, potentially enabling lateral movement attacks where attackers can escalate privileges and access critical systems. The vulnerability particularly affects enterprises that rely heavily on remote access solutions, as the GlobalProtect service provides the primary interface for secure remote connections to corporate networks. Security professionals must consider that this vulnerability can be exploited without authentication, making it particularly dangerous in environments where network monitoring is insufficient or where firewalls are configured to allow extensive access to the GlobalProtect service. The impact is further compounded by the fact that this vulnerability affects multiple major PAN-OS version lines, meaning that organizations across different security tiers and operational environments may be simultaneously at risk, requiring coordinated patch management efforts across the entire organization.
Organizations should immediately implement mitigations that align with both industry best practices and the specific requirements of the ATT&CK framework's technique T1071.004 for application layer protocol: DNS. The recommended approach includes applying the official PAN-OS patches released by Palo Alto Networks, which address the XML parsing logic and implement proper input validation for external entity references. Network administrators should also consider implementing additional protective measures such as disabling unnecessary GlobalProtect services, implementing strict XML validation rules, and monitoring for suspicious XML traffic patterns. The mitigation strategy should incorporate network segmentation to limit access to GlobalProtect interfaces, particularly for external-facing systems. Organizations should also enhance their monitoring capabilities to detect potential exploitation attempts through unusual XML processing activities or unauthorized network requests originating from the firewall. Furthermore, implementing proper input sanitization and validation procedures for all XML processing components, following the principles outlined in the OWASP XML External Entity Prevention Cheat Sheet, will provide additional defense-in-depth measures against similar vulnerabilities. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date security patches and implementing comprehensive security monitoring solutions that can detect and respond to exploitation attempts across all network components including firewalls and security gateways.