Cisco Web Security Appliance (WSA) Server Name Identification Data Exfiltration (cisco-sa-sni-data-exfil-mFgzXqLN)

high Nessus Plugin ID 152812


The remote device is missing a vendor-supplied security patch.


According to its self-reported version, Cisco Web Security Appliance (WSA) is affected by a vulnerability in Server Name Identification (SNI) request filtering that allows an unauthenticated, remote attacker to bypass filtering technology on an affected device and exfiltrate data from a compromised host. This vulnerability is due to inadequate filtering of the SSL handshake. An attacker could exploit this vulnerability by using data from the SSL client hello packet to communicate with an external server. A successful exploit could allow the attacker to execute a command-and-control attack on a compromised host and perform additional data exfiltration attacks.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.


Upgrade to the relevant fixed version referenced in Cisco bug IDs CSCvy50873

See Also

Plugin Details

Severity: High

ID: 152812

File Name: cisco-sa-sni-data-exfil-mFgzXqLN.nasl

Version: 1.6

Type: combined

Family: CISCO

Published: 8/25/2021

Updated: 8/27/2021

Supported Sensors: Nessus

Risk Information


Risk Factor: Medium

Score: 4.4


Risk Factor: Medium

Base Score: 5

Temporal Score: 3.7

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:P/A:N

CVSS Score Source: CVE-2021-34749


Risk Factor: High

Base Score: 8.6

Temporal Score: 7.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/h:cisco:web_security_appliance, cpe:/a:cisco:web_security_appliance, cpe:/o:cisco:web_security_appliance, cpe:/o:cisco:asyncos

Required KB Items: Host/AsyncOS/Cisco Web Security Appliance/DisplayVersion, Host/AsyncOS/Cisco Web Security Appliance/Version

Exploit Ease: No known exploits are available

Patch Publication Date: 8/18/2021

Vulnerability Publication Date: 8/18/2021

Reference Information

CVE: CVE-2021-34749

CISCO-SA: cisco-sa-sni-data-exfil-mFgzXqLN

IAVA: 2021-A-0393