Cisco VPN Client zero-length IKE packet payload denial of service

cisco-vpn-zerolength-dos (9821) The risk level is classified as MediumMedium Risk


The Cisco Virtual Private Network (VPN) Client software is vulnerable to a denial of service attack, caused by improper handling of specially-malformed packets. If a remote attacker sends a specially-crafted IKE packet with a zero-length payload to a vulnerable VPN Client, the attacker could cause the CPU usage to increase to 100%, which would cause a denial of service against the affected system.


Denial of Service


Upgrade to the latest version of Cisco VPN Client software (3.6 or later), as listed in Cisco Security Advisory: Cisco VPN Client Multiple Vulnerabilities. See References.

For FreeBSD Ports Collection:
Upgrade to the latest ports collection, as listed in FreeBSD Security Notice FreeBSD-SN-02:05. See References.

For OpenBSD 3.1:
Apply the patch for this vulnerability, as listed in OpenBSD 010: RELIABILITY FIX: July 5, 2002. See References.

For other distributions:
Contact your vendor for upgrade or patch information.


Platforms Affected:

  • Cisco VPN Client 3.5.1
  • Cisco VPN Client 3.5.2


Aug 12, 2002

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