PT-2021-4467 · Cisco · Cisco Ios Xe+1

Austin Martinetti · Published 2021-09-22 · Updated 2025-10-30 · CVE-2021-34705

Positive Technologies (AI Summary)

CVSS v3.1

5.3

Medium

Base vector

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

Name of the Vulnerable Software and Affected Versions Cisco IOS Software and Cisco IOS XE Software (affected versions not specified)

Description A vulnerability in the Voice Telephony Service Provider (VTSP) service could allow an unauthenticated, remote attacker to bypass configured destination patterns and dial arbitrary numbers. This issue 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.

Recommendations At the moment, there is no information about a newer version that contains a fix for this vulnerability.

Weakness Enumeration

CWE-232

Related Identifiers

BDU:2021-05100

CVE-2021-34705

Affected Products

Cisco Ios

Cisco Ios Xe

References · 9

• https://osv.dev/vulnerability/CVE-2021-34705 · Vendor Advisory
• https://bdu.fstec.ru/vul/2021-05100 · Security Note
• https://nvd.nist.gov/vuln/detail/CVE-2021-34705 · Security Note
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fxo-pattern-bypass-jUXgygYv · Vendor Advisory
• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fxo-pattern-bypass-jUXgygYv · Vendor Advisory
• https://t.me/cibsecurity/29262 · Telegram Post
• https://t.me/cveNotify/141050 · Telegram Post
• https://t.me/cvenotify/22128 · Telegram Post
• https://t.me/cvenotify/70461 · Telegram Post