Denial of service in Cisco Web Security Appliance

1) Input validation error

EUVDB-ID: #VU19021

Risk: High

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber]

CVE-ID: CVE-2019-1886

CWE-ID: CWE-20 - Improper input validation

Exploit availability: No

Description

The vulnerability allows an unauthenticated, remote attacker to cause a denial of service (DoS) condition.

The vulnerability exist due to insufficient validation of Secure Sockets Layer (SSL) server certificates in the HTTPS decryption feature. A remote attacker can install a malformed certificate in a web server, send a request to it through the Cisco WSA and cause an unexpected restart of the proxy process on an affected device.

Mitigation

Install update from vendor's website.

Vulnerable software versions

Cisco AsyncOS for Web Security Appliances: 10.5 - 11.5

CPE2.3

• cpe:2.3:a:cisco_systems:cisco_asyncos_for_web_security_appliances:10.5:*:*:*:*:*:*:*
• cpe:2.3:a:cisco_systems:cisco_asyncos_for_web_security_appliances:11.5:*:*:*:*:*:*:*

External links

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190703-wsa-dos

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

How the attacker can exploit this vulnerability?

The attacker would have to send a specially crafted request to the affected application in order to exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

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