*IMPORTANT – PLEASE READ* ASA/FTD Software RSA Private Key Leak Vulnerability

A vulnerability in the handling of RSA keys on devices running Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to retrieve an RSA private key.

This vulnerability is due to a logic error when the RSA key is stored in memory on a hardware platform that performs hardware-based cryptography. An attacker could exploit this vulnerability by using a Lenstra side-channel attack against the targeted device. A successful exploit could allow the attacker to retrieve the RSA private key.

This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-rsa-key-leak-Ms7UEfZz

 

If an RSA key is flagged by the Cisco off-box detection script or any of the conditions noted in the Indicators of Compromise section of this advisory, Cisco recommends that the RSA key be replaced and any certificates that use this RSA key pair be revoked and replaced. The following Cisco ASA and FTD Software features are known to be used with a configured RSA key; however, any flagged RSA key should be replaced on the device.

The following conditions may be observed on an affected device:

  • This vulnerability will apply to approximately 5 percent of the RSA keys on a device that is running a vulnerable release of Cisco ASA Software or Cisco FTD Software; not all RSA keys are expected to be affected due to mathematical calculations applied to the RSA key.
  • The RSA key could be valid but have specific characteristics that make it vulnerable to the potential leak of the RSA private key. If an attacker obtains the RSA private key, they could use the key to impersonate a device that is running Cisco ASA Software or Cisco FTD Software or to decrypt the device traffic.
  • The RSA key could be malformed and invalid. A malformed RSA key is not functional, and a TLS client connection to a device that is running Cisco ASA Software or Cisco FTD Software that uses the malformed RSA key will result in a TLS signature failure, which means a vulnerable software release created an invalid RSA signature that failed verification. If an attacker obtains the RSA private key, they could use the key to impersonate a device that is running Cisco ASA Software or Cisco FTD Software or to decrypt the device traffic.

Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

  • This vulnerability affects the following Cisco products, which perform hardware-based cryptographic functions, if they are running a vulnerable release of Cisco ASA Software or Cisco FTD Software:

    • ASA 5506-X with FirePOWER Services
    • ASA 5506H-X with FirePOWER Services
    • ASA 5506W-X with FirePOWER Services
    • ASA 5508-X with FirePOWER Services
    • ASA 5516-X with FirePOWER Services
    • Firepower 1000 Series Next-Generation Firewall
    • Firepower 2100 Series Security Appliances
    • Firepower 4100 Series Security Appliances
    • Firepower 9300 Series Security Appliances
    • Secure Firewall 3100

     

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