CVE-2018-8753 in cOS Core
Summary
by MITRE
The IKEv1 implementation in Clavister cOS Core before 11.00.11, 11.20.xx before 11.20.06, and 12.00.xx before 12.00.09 allows remote attackers to decrypt RSA-encrypted nonces by leveraging a Bleichenbacher attack.
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Analysis
by VulDB Data Team • 03/16/2020
The vulnerability identified as CVE-2018-8753 represents a critical cryptographic flaw in the Internet Key Exchange version 1 implementation within Clavister cOS Core firewall software. This issue affects multiple version ranges including releases before 11.00.11, 11.20.06, and 12.00.09, creating a persistent security risk across various network infrastructure deployments. The vulnerability specifically targets the RSA encryption handling during IKEv1 key exchange processes, where the system fails to properly validate cryptographic padding mechanisms. This weakness enables remote attackers to exploit a well-known cryptographic attack vector known as the Bleichenbacher attack, which targets PKCS#1 v1.5 padding validation errors in RSA implementations.
The technical flaw stems from improper implementation of RSA padding validation during the IKEv1 authentication phase, where the system does not adequately protect against timing attacks or padding oracle vulnerabilities. When the IKEv1 protocol attempts to decrypt nonces using RSA encryption, the flawed implementation provides exploitable feedback through timing variations or error responses that reveal information about the validity of padding attempts. This vulnerability is classified under CWE-327, which specifically addresses the use of weak cryptographic algorithms and improper implementation of cryptographic padding schemes. The attack leverages the mathematical properties of RSA encryption combined with the predictable error responses from the vulnerable system to iteratively reconstruct the encrypted nonce values without possessing the private key.
Operationally, this vulnerability poses severe implications for network security infrastructure as it allows remote attackers to potentially decrypt sensitive communications and compromise the integrity of the IKEv1 key exchange process. The Bleichenbacher attack requires multiple attempts and can be automated, making it particularly dangerous in environments where IKEv1 is actively used for VPN connections and secure network communications. Successful exploitation could lead to unauthorized access to encrypted network traffic, potential man-in-the-middle attacks, and complete compromise of the IPsec security associations established through IKEv1. The vulnerability affects organizations relying on Clavister firewalls for network security, particularly those with active IKEv1 implementations in their security infrastructure, creating a significant risk for enterprise networks and service providers.
Organizations should immediately implement mitigations including updating to the patched versions of Clavister cOS Core software, disabling IKEv1 protocols where possible, and implementing additional monitoring for suspicious authentication attempts. The recommended remediation strategy aligns with ATT&CK technique T1566 which focuses on credential harvesting through network protocol manipulation. Security teams should also consider implementing network segmentation to limit the attack surface and regularly audit their IKEv1 usage to identify and phase out vulnerable configurations. The vulnerability demonstrates the critical importance of proper cryptographic implementation and validation, as highlighted in NIST SP 800-57 guidelines regarding key management and cryptographic algorithm selection. Organizations should also review their overall cryptographic posture and consider migrating to more secure protocols such as IKEv2 which provides better protection against these types of padding oracle attacks.