CVE-2018-17540 in strongSwan
Summary
by MITRE
The gmp plugin in strongSwan before 5.7.1 has a Buffer Overflow via a crafted certificate.
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Analysis
by VulDB Data Team • 05/22/2023
The vulnerability identified as CVE-2018-17540 represents a critical buffer overflow flaw within the gmp plugin of strongSwan IPsec implementation. This issue affects versions prior to 5.7.1 and specifically targets the handling of crafted certificates within the cryptographic operations framework. The gmp plugin serves as a crucial component for managing cryptographic operations using the GNU Multiple Precision Arithmetic Library, making it a prime target for exploitation in cryptographic contexts. The vulnerability arises from insufficient input validation and boundary checking when processing specially crafted X.509 certificates that contain malformed extensions or oversized data structures. This buffer overflow condition occurs during the certificate parsing process where the plugin fails to properly validate the size of certificate fields before attempting to copy data into fixed-size buffers, creating an exploitable condition that could allow attackers to overwrite adjacent memory locations. The flaw is particularly concerning because strongSwan is widely deployed in enterprise environments for secure communications, VPN implementations, and network security infrastructure. When exploited, this vulnerability could enable attackers to execute arbitrary code on systems running vulnerable versions of strongSwan, potentially leading to complete system compromise and unauthorized access to sensitive network communications.
The technical nature of this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions where insufficient boundary checks allow attackers to overwrite adjacent memory locations. The attack vector specifically targets the certificate processing pipeline within the gmp plugin, where certificate data is parsed and validated before being used in cryptographic operations. The operational impact extends beyond simple code execution as the vulnerability could be leveraged to bypass authentication mechanisms, decrypt sensitive communications, or establish persistent backdoors within secured networks. This type of vulnerability is particularly dangerous in environments where strongSwan is used for site-to-site VPN connections, remote access services, or any infrastructure requiring robust cryptographic security. The exploitation requires an attacker to present a specially crafted certificate to a vulnerable strongSwan instance, making it a server-side vulnerability that can be triggered through legitimate certificate exchange processes during IKE (Internet Key Exchange) protocol negotiations. The vulnerability demonstrates the importance of proper input validation in cryptographic libraries and highlights the risks associated with complex certificate handling procedures in security infrastructure software.
Mitigation strategies for CVE-2018-17540 primarily focus on upgrading to strongSwan version 5.7.1 or later, which includes patched buffer validation routines and improved certificate parsing mechanisms. Organizations should implement immediate patch management procedures to update all affected strongSwan installations across their network infrastructure. Additionally, network administrators should consider implementing certificate monitoring and validation procedures to detect and prevent the acceptance of malformed certificates in production environments. The vulnerability also underscores the importance of following security best practices such as implementing principle of least privilege for cryptographic operations and regularly auditing certificate management processes. From an ATT&CK framework perspective, this vulnerability maps to T1059.007 for command and control through compromised VPN infrastructure and T1566 for initial access via malicious certificate delivery. Organizations should also consider implementing network segmentation and monitoring to detect unusual certificate exchange patterns that might indicate exploitation attempts. The incident highlights the critical need for maintaining up-to-date cryptographic libraries and the importance of thorough security testing of cryptographic components in security infrastructure software. Regular security assessments and vulnerability scanning should include checks for similar buffer overflow conditions in other cryptographic libraries and plugins within the broader security ecosystem.