CVE-2017-15638 in SuSEfirewall2
Summary
by MITRE
The SuSEfirewall2 package before 3.6.312-2.13.1 in SUSE Linux Enterprise (SLE) Desktop 12 SP2, Server 12 SP2, and Server for Raspberry Pi 12 SP2; before 3.6.312.333-3.10.1 in SLE Desktop 12 SP3 and Server 12 SP3; before 3.6_SVNr208-2.18.3.1 in SLE Server 11 SP4; before 3.6.312-5.9.1 in openSUSE Leap 42.2; and before 3.6.312.333-7.1 in openSUSE Leap 42.3 might allow remote attackers to bypass intended access restrictions on the portmap service by leveraging a missing source net restriction for _rpc_ services.
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Analysis
by VulDB Data Team • 12/05/2019
The vulnerability identified as CVE-2017-15638 affects the SuSEfirewall2 package across multiple SUSE Linux Enterprise and openSUSE distributions, representing a significant security weakness in network access control mechanisms. This flaw specifically targets the portmap service, which serves as a crucial component in network communication by mapping RPC (Remote Procedure Call) program numbers to network ports. The vulnerability stems from an insufficient implementation of source network restrictions for rpc services, creating a pathway for unauthorized network access that directly undermines the firewall's intended protection boundaries. Such a weakness represents a critical failure in the principle of least privilege and network segmentation that security administrators rely upon to protect system resources.
The technical nature of this vulnerability manifests through the absence of proper source address validation for RPC services within the firewall configuration. When the SuSEfirewall2 package processes rules for RPC services, it fails to enforce mandatory source network restrictions that should prevent unauthorized systems from accessing the portmap service. This missing validation allows remote attackers to bypass access controls by directly connecting to RPC services without proper authentication or source verification, effectively creating a backdoor through the firewall's protective mechanisms. The flaw is particularly concerning because RPC services are fundamental to many network operations including file sharing, remote administration, and system management functions that require strict access controls.
From an operational perspective, this vulnerability enables remote attackers to exploit the portmap service without proper authorization, potentially leading to unauthorized access to underlying RPC services that may provide elevated privileges or sensitive system information. The impact extends beyond simple network access, as successful exploitation could allow attackers to discover and potentially manipulate other services running on the same system or network segment. This vulnerability aligns with CWE-668, which describes "Exposure of Resource to Wrong Sphere" and represents a classic case of insufficient access control enforcement. The operational risk is amplified by the fact that portmap services are often used as entry points for more complex attacks, making this vulnerability a potential gateway for privilege escalation or lateral movement within network environments.
The security implications of this vulnerability extend to the broader attack surface of systems running affected versions of SuSEfirewall2, as it directly contradicts fundamental network security principles established by frameworks such as the MITRE ATT&CK matrix where network infiltration and service enumeration represent common initial access techniques. Organizations utilizing these vulnerable distributions face increased risk of unauthorized system access, data exfiltration, and potential compromise of critical infrastructure components that rely on RPC services for communication. The vulnerability's persistence across multiple SUSE releases demonstrates a systemic issue in firewall rule implementation that requires immediate remediation through package updates, patch management processes, and verification of network access controls to ensure proper enforcement of source restrictions for RPC services.
Mitigation strategies for this vulnerability must include immediate deployment of updated SuSEfirewall2 packages to versions 3.6.312-2.13.1 and later for SUSE Linux Enterprise 12 SP2, 3.6.312.333-3.10.1 for SUSE Linux Enterprise 12 SP3, 3.6_SVNr208-2.18.3.1 for SLE Server 11 SP4, 3.6.312-5.9.1 for openSUSE Leap 42.2, and 3.6.312.333-7.1 for openSUSE Leap 42.3. Additionally, system administrators should conduct thorough network audits to verify that RPC service access controls are properly configured, implement network segmentation to limit RPC service exposure, and establish monitoring procedures to detect unauthorized access attempts to portmap and RPC services. The remediation process should also include verification that source network restrictions are properly enforced for all RPC services to prevent similar vulnerabilities from occurring in other network access control implementations.