Cyber Resilience

CVE-2021-34705

Medium

Published: 23 September 2021

Published
23 September 2021
Modified
30 October 2025
KEV Added
Patch
CVSS Score v3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
EPSS Score 0.0055 68.5th percentile
Risk Priority 11 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2021-34705 is a medium-severity Improper Handling of Undefined Values (CWE-232) vulnerability in Cisco Ios. Its CVSS base score is 5.3 (Medium).

Operationally, ranked in the top 31.5% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability details

A vulnerability in the Voice Telephony Service Provider (VTSP) service of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to bypass configured destination patterns and dial arbitrary numbers. This vulnerability is due to insufficient…

more

validation of dial strings at Foreign Exchange Office (FXO) interfaces. An attacker could exploit this vulnerability by sending a malformed dial string to an affected device via either the ISDN protocol or SIP. A successful exploit could allow the attacker to conduct toll fraud, resulting in unexpected financial impact to affected customers.

CWE(s)

Related Threats

No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.

Affected Assets

cisco
ios
12.3\(10\), 12.3\(10a\), 12.3\(10a\)m0, 12.3\(10b\), 12.3\(10c\)
cisco
ios xe
16.1.1, 16.1.2, 16.1.3, 16.10.1, 16.10.1a

Mitigating Controls

No mitigating controls mapped yet. The per-CVE control annotator has not reached this CVE.

References