CVE-2018-0131 in IOS
Summary
by MITRE
A vulnerability in the implementation of RSA-encrypted nonces in Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to obtain the encrypted nonces of an Internet Key Exchange Version 1 (IKEv1) session. The vulnerability exists because the affected software responds incorrectly to decryption failures. An attacker could exploit this vulnerability sending crafted ciphertexts to a device configured with IKEv1 that uses RSA-encrypted nonces. A successful exploit could allow the attacker to obtain the encrypted nonces. Cisco Bug IDs: CSCve77140.
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Analysis
by VulDB Data Team • 05/02/2023
The vulnerability identified as CVE-2018-0131 represents a critical weakness in the cryptographic implementation of Internet Key Exchange Version 1 within Cisco IOS and IOS XE software platforms. This flaw specifically targets the handling of RSA-encrypted nonces during IKEv1 session establishment, creating a pathway for remote attackers to extract sensitive cryptographic data without requiring authentication credentials. The vulnerability stems from improper error handling mechanisms within the software's cryptographic processing routines, where the system fails to properly manage decryption failures that occur during IKEv1 nonce processing. This misconfiguration allows attackers to exploit the software's response to malformed ciphertext inputs, effectively enabling information disclosure through carefully crafted attack vectors.
The technical exploitation of this vulnerability occurs through the manipulation of IKEv1 protocol messages containing RSA-encrypted nonces. When the affected Cisco devices receive malformed ciphertext data, the software's cryptographic subsystem does not properly handle the decryption failure conditions, instead revealing information about the encrypted nonce values. This behavior creates a side-channel information leak that can be systematically exploited by attackers to reconstruct or predict nonce values used in IKEv1 negotiations. The vulnerability specifically affects devices configured with IKEv1 implementations that rely on RSA encryption for nonce protection, making it particularly relevant to enterprise networks utilizing Cisco routers and switches that support this legacy protocol version. The flaw aligns with CWE-209, which describes improper handling of exception conditions, and demonstrates how cryptographic error handling can create security weaknesses in network infrastructure devices.
Operationally, this vulnerability poses significant risks to network security infrastructure as it enables attackers to gather information that could facilitate more sophisticated attacks against IKEv1 sessions. The extracted nonce information could potentially be used to conduct replay attacks, session hijacking attempts, or to weaken the overall cryptographic security posture of the network. Since IKEv1 is commonly used for establishing secure communication channels between network devices and remote access clients, the compromise of nonce values could undermine the integrity of IPsec tunnels and VPN connections. The vulnerability's remote exploitability means that attackers can target affected devices from outside the network perimeter, making it particularly dangerous for organizations with exposed Cisco devices. This weakness also correlates with ATT&CK technique T1552.001, which covers unsecured credentials, as the leaked nonce information can be used to compromise authentication processes within the IPsec framework.
Organizations should implement immediate mitigations including applying the relevant Cisco security patches and updates that address the cryptographic error handling issues in the IKEv1 implementation. Network administrators should consider disabling IKEv1 on affected devices where possible and migrating to IKEv2, which provides better cryptographic security and is less susceptible to this particular class of vulnerability. Additional protective measures include implementing network segmentation to limit exposure of affected devices, monitoring for unusual IKEv1 traffic patterns, and conducting thorough network assessments to identify all potentially vulnerable Cisco devices. The vulnerability highlights the critical importance of proper cryptographic implementation and error handling in network security infrastructure, particularly when dealing with protocol elements that are fundamental to secure communications. Organizations should also consider implementing intrusion detection systems that can identify and alert on suspicious IKEv1 traffic patterns that may indicate exploitation attempts.