Authorization bypass in Cisco ASR 5000 Series Software

Published: 2021-06-02

Risk	Medium
Patch available	YES
Number of vulnerabilities	2
CVE-ID	CVE-2021-1539 CVE-2021-1540
CWE-ID	CWE-285
Exploitation vector	Network
Public exploit	N/A
Vulnerable software	Cisco Virtualized Packet Core Client/Desktop applications / Virtualization software Cisco StarOS Operating systems & Components / Operating system Cisco ASR 5000 Series Hardware solutions / Firmware
Vendor	Cisco Systems, Inc

Security Bulletin

This security bulletin contains information about 2 vulnerabilities.

1) Improper Authorization

EUVDB-ID: #VU53746

Risk: Medium

CVSSv4.0: 5.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-1539

CWE-ID: CWE-285 - Improper Authorization

Exploit availability: No

Description

The vulnerability allows a remote user to gain unauthorized access to the system.

The vulnerability exists in the authorization process of Cisco ASR 5000 Series Software (StarOS) due to incorrect authorization of non-interactive CLI commands. A remote authenticate user can bypass TACACS authorization by sending a crafted Secure Shell (SSH) request to an affected device and execute a certain CLI commands.

Successful exploitation of the vulnerability may result in unauthorized access to sensitive information or denial of service condition.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Cisco Virtualized Packet Core: All versions

Cisco StarOS: before 21.16.9

CPE2.3

External links

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asr5k-autho-bypass-mJDF5S7n
https://bst.cloudapps.cisco.com/bugsearch/bug/CSCvu85001

Q & A

Can this vulnerability be exploited remotely?

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

How the attacker can exploit this vulnerability?

The attacker would have to trick the victim to open a a specially crafted file.

Is there known malware, which exploits this vulnerability?

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

2) Improper Authorization

EUVDB-ID: #VU53747