CVE-2026-50752: Certificate Validation Bypass in VPN Site-to-Site Connections Using IKEv1

Synopsis

A certificate validation bypass affects the IKEv1 key exchange implementation in Check Point Quantum Security Gateway and Spark Firewall products. An unauthenticated attacker with a man-in-the-middle position on the network path can bypass certificate-based authentication for VPN site-to-site connections, exploiting a flaw that only requires high attack complexity due to the positional requirement. Successful exploitation allows the attacker to intercept or modify traffic that was expected to be protected inside the VPN tunnel. No fix versions have been published yet; HarborGuard is tracking the advisory for patch availability.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker must be positioned on the network path between the two VPN peers to intercept and manipulate IKEv1 key exchange traffic over the network.

• AuthenticationNot required

  No credentials or account are needed; the attacker exploits the validation flaw before any authenticated session is established.

• Victim interactionNot required

  No action by a user or administrator is required; exploitation targets the automated IKEv1 handshake between gateway peers.

• Attack complexityDetail

  Attack complexity is rated High because the attacker must successfully achieve a man-in-the-middle position on the network path between the two VPN endpoints, which depends on environmental factors beyond the attacker's direct control.

Blast Radius

• Reads plaintext contents of traffic that was expected to be encrypted inside the VPN tunnel, including credentials, session data, and application payloads transiting the site-to-site connection.
• Modifies in-transit data between VPN sites without either endpoint detecting the tampering, enabling injection of malicious payloads into otherwise trusted internal traffic.
• Undermines the trust model of certificate-based peer authentication, allowing an adversary to impersonate a legitimate VPN peer gateway to one or both sides of the connection.