UDP Remote Access

Port 500 (IKE/IPSec)

Learn about port 500 (IKE/IPSec) - security risks, vulnerabilities, and common uses. Find devices with port 500 open.

Quick Info

Port Number

500

Protocol

UDP

Service

IKE/IPSec

IANA Name

IKE/IPSec

Service Description

UDP port 500 is primarily associated with Internet Key Exchange (IKE), which is a crucial component of the Internet Protocol Security (IPSec) protocol suite. IKE is a key management protocol used to establish secure, authenticated communication channels between two parties, typically over a network. It negotiates and establishes Security Associations (SAs) which define the cryptographic algorithms and parameters used to encrypt and authenticate network traffic. The protocol operates in two phases: Phase 1 establishes a secure channel between the two peers, often using pre-shared keys, digital signatures, or public key encryption, and Phase 2 negotiates the IPSec SAs used to protect the actual data traffic.

Historically, IKE evolved from earlier key exchange protocols and was standardized to provide a robust and interoperable method for securing IP-based communications. The initial version of IKE (IKEv1) was later succeeded by IKEv2, which offers improvements in efficiency, reliability, and security. IKEv2 typically uses UDP port 500 for the initial exchange, but may switch to UDP port 4500 when traversing Network Address Translation (NAT) devices. The technical details involve complex negotiation processes using various proposals and transforms to agree on encryption algorithms (e.g., AES, 3DES), hash functions (e.g., SHA1, SHA256), authentication methods (e.g., pre-shared keys, RSA signatures), and Diffie-Hellman groups for key exchange.

## Firewall Recommendations

If you are not using IPSec VPN, block UDP port 500 on your firewall. If you are using IPSec VPN, restrict access to UDP port 500 to only the necessary IP addresses. Use strong pre-shared keys or digital certificates for authentication. Regularly update your VPN software to patch security vulnerabilities. Implement intrusion detection and prevention systems to monitor for suspicious activity on port 500. Consider using IKEv2 instead of IKEv1, as it offers improved security features. Implement rate limiting to mitigate DoS attacks. Ensure proper configuration of NAT traversal to avoid issues with port 4500.

Security Information

Port 500 is a common target for attackers because it's the entry point for establishing VPN connections. Vulnerabilities in IKE implementations can lead to authentication bypass, denial-of-service (DoS) attacks, and even the ability to decrypt VPN traffic. Weak pre-shared keys are a significant risk, as they can be cracked through brute-force or dictionary attacks. Furthermore, misconfigurations in IKE policies, such as allowing weak encryption algorithms or insecure authentication methods, can weaken the overall security of the VPN connection. Attackers may also exploit vulnerabilities in IKE parsing or processing to execute arbitrary code on the VPN gateway or client. DoS attacks can flood the port with invalid IKE packets, overwhelming the VPN server and preventing legitimate users from connecting.

Known Vulnerabilities

CVE	Name	Severity	Description
CVE-2015-8023	StrongSwan IKEv1 Aggressive Mode Vulnerability	High	Уязвимость в StrongSwan IKEv1 в агрессивном режиме позволяет злоумышленникам удаленно получить доступ к защищенной сети.
CVE-2017-17492	Libreswan IKEv2 Fragmentation Vulnerability	Medium	Libreswan IKEv2 не проверяет корректно фрагментированные пакеты IKEv2, что может позволить вызвать отказ в обслуживании.
CVE-2018-5394	FragmentSmack: IP Fragmentation Attack	High	Уязвимость, связанная с обработкой фрагментированных IP-пакетов, приводящая к истощению ресурсов и отказу в обслуживании. Хотя и не специфична только для порта 500, но может быть использована для атак на IKE/IPsec.
CVE-2022-32206	Linux Kernel Netfilter vulnerability	Critical	Уязвимость в подсистеме Netfilter ядра Linux, которая может быть использована для обхода фильтров брандмауэра и потенциально для удаленного выполнения кода. При использовании IPsec, может быть использована для обхода правил, предназначенных для защиты трафика IPsec.