CVE-2021-34713

Cisco IOS XR Software for ASR 9000 Series Routers Denial of Service Vulnerability

HIGH

7.4

CVSS Score

Published: September 9, 2021 at 05:00 AM UTC

Updated: June 17, 2026 at 03:56 AM UTC

14 products affected across 1 vendorIOS XrAsr 9010Asr 9904

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Severity

HIGH7.4

Exploit prediction

EPSS 0.4%

SSVC

No known exploit

Description

A vulnerability in the Layer 2 punt code of Cisco IOS XR Software running on Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, adjacent attacker to cause the affected line card to reboot. This vulnerability is due to incorrect handling of specific Ethernet frames that cause a spin loop that can make the network processors unresponsive. An attacker could exploit this vulnerability by sending specific types of Ethernet frames on the segment where the affected line cards are attached. A successful exploit could allow the attacker to cause the affected line card to reboot.

Affected

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

IOS Xr · Cisco

95%

6.4 ≤ v < 6.6.36.7 ≤ v < 6.7.17.0 ≤ v < 7.0.27.1 ≤ v < 7.1.1

Affected range stops below 6.6.3, so it looks safe — our inference, not a vendor statement

Affected range stops below 6.7.1, so it looks safe — our inference, not a vendor statement

Affected range stops below 7.0.2, so it looks safe — our inference, not a vendor statement

Affected range stops below 7.1.1, so it looks safe — our inference, not a vendor statement

cisco-asr-9000 (environment) · cisco-asr-9000v-v2 (environment) · cisco-asr-9001 (environment) · cisco-asr-9006 (environment) · cisco-asr-9010 (environment) · cisco-asr-9901 (environment) · cisco-asr-9902 (environment) · cisco-asr-9903 (environment) · cisco-asr-9904 (environment) · cisco-asr-9906 (environment) · cisco-asr-9910 (environment) · cisco-asr-9912 (environment) · cisco-asr-9922 (environment)

Asr 9000 · Ciscodevice

80%

All versions

Asr 9000V-V2 · Ciscodevice

80%

All versions

Asr 9001 · Ciscodevice

80%

All versions

Asr 9006 · Ciscodevice

80%

All versions