#VU54172 Improper Certificate Validation in Cisco AsyncOS for Web Security Appliances and Cisco AsyncOS for Cisco Email Security Appliance - CVE-2021-1566

Vulnerability identifier: #VU54172

Vulnerability risk: Medium

CVSSv4.0: 1.3 [CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-1566

CWE-ID: CWE-295

Exploitation vector: Local network

Exploit availability: No

Vulnerable software:
Cisco AsyncOS for Web Security Appliances
Server applications / IDS/IPS systems, Firewalls and proxy servers
Cisco AsyncOS for Cisco Email Security Appliance
Server applications / IDS/IPS systems, Firewalls and proxy servers

Vendor: Cisco Systems, Inc

Description

The vulnerability allows a remote attacker to preform MitM attack.

The vulnerability exists due to improper certificate validation when establishing TLS connection. A remote attacker can perform a man-in-the-middle (MitM) attack.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Cisco AsyncOS for Web Security Appliances: before 11.8.3 021

Cisco AsyncOS for Cisco Email Security Appliance: before 12.5.3 035

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External links
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-esa-wsa-cert-vali-n8L97RW
https://bst.cloudapps.cisco.com/bugsearch/bug/CSCvw08342
https://bst.cloudapps.cisco.com/bugsearch/bug/CSCvw08378

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the local network (LAN).

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.