CVE-2002-1623 in Firewall-1
Summary
by MITRE
The design of the Internet Key Exchange (IKE) protocol, when using Aggressive Mode for shared secret authentication, does not encrypt initiator or responder identities during negotiation, which may allow remote attackers to determine valid usernames by (1) monitoring responses before the password is supplied or (2) sniffing, as originally reported for FireWall-1 SecuRemote.
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Analysis
by VulDB Data Team • 09/03/2025
The Internet Key Exchange protocol version 1 as implemented in various security products including FireWall-1 SecuRemote contains a fundamental design flaw that exposes sensitive authentication information during the initial negotiation phase. This vulnerability specifically affects the aggressive mode of IKE implementation where shared secret authentication is employed, creating a critical weakness in the protocol's security architecture. The flaw stems from the protocol's decision to transmit identity information in plaintext during the initial exchange, before the actual authentication credentials are processed, thereby compromising the confidentiality of user identities.
The technical implementation of this vulnerability occurs during the IKE aggressive mode negotiation process where the initiator and responder exchange identity information without encryption. This design decision allows attackers to capture network traffic during the initial phase of the key exchange and extract username information directly from the packets. The vulnerability manifests because the protocol does not establish a secure channel for identity transmission until after the authentication process has been completed, creating a window of opportunity for passive network monitoring attacks. This weakness is particularly pronounced in environments where network traffic is easily accessible through packet sniffing operations or when attackers can monitor traffic before the actual password authentication occurs.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the capability to enumerate valid user accounts within the system. This reconnaissance capability allows malicious actors to identify legitimate users, which can then be targeted for further attacks including password spraying, brute force attempts, or social engineering operations. The vulnerability is particularly dangerous in environments where user accounts are not properly secured or where weak authentication mechanisms are in place. The exposure of user identities can also facilitate targeted attacks against specific individuals within an organization, making this vulnerability a significant threat to overall security posture. This weakness directly relates to CWE-310 and CWE-312, which address cryptographic weaknesses and the exposure of sensitive information through improper encryption practices.
Mitigation strategies for this vulnerability require a fundamental shift in the IKE implementation approach. Organizations should implement the main mode of IKE instead of aggressive mode whenever possible, as main mode encrypts identity information during negotiation. The use of stronger authentication mechanisms such as certificate-based authentication rather than shared secrets can also provide protection against this specific vulnerability. Network administrators should also consider implementing additional monitoring and detection capabilities to identify potential exploitation attempts. The implementation of proper network segmentation and access controls can help limit the damage from successful exploitation attempts. Security professionals should also ensure that all systems using IKE are updated with the latest security patches and that configurations are reviewed to eliminate the use of aggressive mode where it is not absolutely necessary. This vulnerability demonstrates the importance of considering the full attack surface during protocol design and highlights the need for proper cryptographic implementation in security-critical systems. The attack vector for this vulnerability aligns with techniques described in the ATT&CK framework under credential access and reconnaissance phases, making it a significant concern for organizations implementing network security solutions that rely on IKE for secure communications.