Vulnerability identifier: #VU51726

Vulnerability risk: Low

CVSSv3.1: 3.8 [CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-1356

CWE-ID: CWE-400

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Cisco Wireless LAN Controller
Hardware solutions / Firmware
Cisco Catalyst 9800 Series Wireless Controllers
Hardware solutions / Routers & switches, VoIP, GSM, etc
Cisco IOS XE
Operating systems & Components / Operating system

Vendor: Cisco Systems, Inc

Description

The vulnerability allows a remote user to perform a denial of service (DoS) attack.

The vulnerability exists due to application does not properly control consumption of internal resources within the web UI of Cisco IOS XE Software. A remote authenticated user can send specially crafted  HTTP requests to the web UI and cause the web management software to hang and consume all available vty lines, preventing new session establishment.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Cisco Wireless LAN Controller: All versions

Cisco Catalyst 9800 Series Wireless Controllers: All versions

Cisco IOS XE: 17.2.1

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External links
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-xe-webui-dos-z9yqYQAn
http://bst.cloudapps.cisco.com/bugsearch/bug/CSCvu94117

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the Internet.

Is there known malware, which exploits this vulnerability?

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