CVE-2022-20866
Published: 10 August 2022
Summary
CVE-2022-20866 is a high-severity Observable Discrepancy (CWE-203) vulnerability in Cisco Adaptive Security Appliance Software. Its CVSS base score is 7.4 (High).
Operationally, ranked in the top 7.2% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
Deeper analysis
A vulnerability in the handling of RSA keys affects devices running Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software. It stems from a logic error that occurs when an RSA key is stored in memory on hardware platforms performing hardware-based cryptography, enabling exposure of the private key material. The flaw impacts roughly 5 percent of RSA keys on vulnerable releases, with affected keys either exhibiting characteristics that permit leakage or being malformed and invalid.
An unauthenticated remote attacker can exploit the issue via a Lenstra side-channel attack against an affected device. Successful exploitation allows retrieval of the RSA private key, which can then be used to impersonate the device or decrypt its traffic; malformed keys additionally produce TLS signature verification failures on client connections.
The Cisco Security Advisory at https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-rsa-key-leak-Ms7UEfZz addresses the vulnerability and provides indicators of compromise for detecting vulnerable keys. The associated EPSS score has remained low, with a current value of 0.0892 and a peak of 0.0985.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2022-26116
Vulnerability details
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…
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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. 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. See the Indicators of Compromise section for more information on the detection of this type of RSA key. 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.
- CWE(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Misdirection can normalize or falsify responses to eliminate observable discrepancies that aid reconnaissance.
Observable discrepancies in system behavior can be modulated to create covert storage or timing channels; the required analysis detects and constrains such avenues.
Prevents attackers from using observable differences in error responses to infer internal system details or state.