CVE-2020-3511

Cisco IOS and IOS XE Software ISDN Q.931 Denial of Service Vulnerability

HIGH

7.4

CVSS Score

Published: September 24, 2020 at 05:51 PM UTC

Updated: June 17, 2026 at 03:18 AM UTC

52 products affected across 1 vendorIOS XeAsr 1002-xAsr 1006

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Severity

HIGH7.4

Exploit prediction

EPSS 0.4%

SSVC

No known exploit

Description

A vulnerability in the ISDN subsystem of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to cause a reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to insufficient input validation when the ISDN Q.931 messages are processed. An attacker could exploit this vulnerability by sending a malicious ISDN Q.931 message to an affected device. A successful exploit could allow the attacker to cause the process to crash, resulting in a reload of the affected device.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

IOS Xe · Cisco

95%

15.1(4)m

cisco-1100-4g-integrated-services-router (environment) · cisco-1100-4gltegb-integrated-services-router (environment) · cisco-1100-4gltena-integrated-services-router (environment) · cisco-1100-4p-integrated-services-router (environment) · cisco-1100-6g-integrated-services-router (environment) · cisco-1100-8p-integrated-services-router (environment) · cisco-1100-integrated-services-router (environment) · cisco-1100-lte-integrated-services-router (environment) · cisco-1101-4p-integrated-services-router (environment) · cisco-1101-integrated-services-router (environment) · cisco-1109-2p-integrated-services-router (environment) · cisco-1109-4p-integrated-services-router (environment) · cisco-1109-integrated-services-router (environment) · cisco-1111x-8p-integrated-services-router (environment) · cisco-1111x-integrated-services-router (environment) · cisco-111x-integrated-services-router (environment) · cisco-1120-integrated-services-router (environment) · cisco-1160-integrated-services-router (environment) · cisco-422-integrated-services-router (environment) · cisco-4321-k9-integrated-services-router (environment) · cisco-4321-k9-rf-integrated-services-router (environment) · cisco-4321-k9-ws-integrated-services-router (environment) · cisco-4331-k9-integrated-services-router (environment) · cisco-4331-k9-rf-integrated-services-router (environment) · cisco-4331-k9-ws-integrated-services-router (environment) · cisco-4351-k9-integrated-services-router (environment) · cisco-4351-k9-rf-integrated-services-router (environment) · cisco-4351-k9-ws-integrated-services-router (environment) · cisco-4431-integrated-services-router (environment) · cisco-4461-integrated-services-router (environment) · cisco-asr-1000-x (environment) · cisco-asr-1001 (environment) · cisco-asr-1001-x (environment) · cisco-asr-1002 (environment) · cisco-asr-1002-x (environment) · cisco-asr-1004 (environment) · cisco-asr-1006 (environment) · cisco-asr-1013 (environment) · cisco-asr1001-hx (environment) · cisco-asr1001-hx-rf (environment) · cisco-asr1001-x (environment) · cisco-asr1001-x-rf (environment) · cisco-asr1001-x-ws (environment) · cisco-asr1002-hx (environment) · cisco-asr1002-hx-rf (environment) · cisco-asr1002-hx-ws (environment) · cisco-asr1002-x (environment) · cisco-asr1002-x-rf (environment) · cisco-asr1002-x-ws (environment) · cisco-csr1000v (environment)

IOS · Cisconpm

60%

All versions

1100-4G Integrated Services Router · Ciscodevice

80%

All versions

1100-4Gltegb Integrated Services Router · Ciscodevice

80%

All versions

1100-4Gltena Integrated Services Router · Ciscodevice

80%

All versions