Vulnerability identifier: #VU56841

Vulnerability risk: Medium

CVSSv3.1: 4.6 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-34705

CWE-ID: CWE-254

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Cisco IOS
Operating systems & Components / Operating system
Cisco IOS XE
Operating systems & Components / Operating system

Vendor: Cisco Systems, Inc

Description

The vulnerability allows a remote attacker to compromise the target system.

The vulnerability exists due to insufficient validation of dial strings at Foreign Exchange Office (FXO) interfaces in the Voice Telephony Service Provider (VTSP) service. A remote attacker can send a specially crafted dial string and conduct toll fraud, resulting in unexpected financial impact to affected customers.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Cisco IOS: 15.1(4)M

Cisco IOS XE: 15.1(4)M

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External links
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fxo-pattern-bypass-jUXgygYv

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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 Internet.

Is there known malware, which exploits this vulnerability?

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