Is CVE-2021-34705 in the CISA KEV catalog?

No. CVE-2021-34705 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-34705?

CVE-2021-34705 has a CVSS v3 base score of 5.3 (MEDIUM).

What is the EPSS score for CVE-2021-34705?

CVE-2021-34705 has an EPSS score of 0.97% (58th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix or mitigate CVE-2021-34705?

No published fix for CVE-2021-34705 has been found yet. Check the linked vendor advisories for guidance as it becomes available.

CVE & CISA-KEV Catalog

CVE-2021-34705

MEDIUM

5.3

CVSS v3

NVD

Description

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 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-232

How to fix

No published remediation has been found for this vulnerability's affected products yet.

Mitigation guidance may be in the linked vendor advisories in the References section below.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityLow

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Exploit Intelligence

0.97%probability of exploitation in 30 days

58thpercentile

Moderate risk: more likely to be exploited than 58% of all known CVEs.

References

Vendor Advisory1

tools.cisco.com

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-10-30.