CVE-2021-34720

Cisco IOS XR Software IP Service Level Agreements and Two-Way Active Measurement Protocol Denial of Service Vulnerability

HIGH

8.6

CVSS Score

Published: September 9, 2021 at 05:01 AM UTC

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

46 products affected across 1 vendorIOS XrAsr 9010Asr 9904

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Severity

HIGH8.6

Exploit prediction

EPSS 1%

SSVC

No known exploit

Description

A vulnerability in the IP Service Level Agreements (IP SLA) responder and Two-Way Active Measurement Protocol (TWAMP) features of Cisco IOS XR Software could allow an unauthenticated, remote attacker to cause device packet memory to become exhausted or cause the IP SLA process to crash, resulting in a denial of service (DoS) condition. This vulnerability exists because socket creation failures are mishandled during the IP SLA and TWAMP processes. An attacker could exploit this vulnerability by sending specific IP SLA or TWAMP packets to an affected device. A successful exploit could allow the attacker to exhaust the packet memory, which will impact other processes, such as routing protocols, or crash the IP SLA process.

Affected

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

IOS Xr · Cisco

95%

v < 6.2.36.3.0 ≤ v < 6.3.26.5.0 ≤ v < 7.2.2

Affected range stops below 6.2.3, so it looks safe — our inference, not a vendor statement

Affected range stops below 6.3.2, so it looks safe — our inference, not a vendor statement

Affected range stops below 7.2.2, so it looks safe — our inference, not a vendor statement

cisco-8101-32fh (environment) · cisco-8101-32h (environment) · cisco-8102-64h (environment) · cisco-8201 (environment) · cisco-8201-32fh (environment) · cisco-8202 (environment) · cisco-8804 (environment) · cisco-8808 (environment) · cisco-8812 (environment) · cisco-8818 (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) · cisco-ncs-1001 (environment) · cisco-ncs-1002 (environment) · cisco-ncs-1004 (environment) · cisco-ncs-4009 (environment) · cisco-ncs-4016 (environment) · cisco-ncs-5001 (environment) · cisco-ncs-5002 (environment) · cisco-ncs-5011 (environment) · cisco-ncs-520 (environment) · cisco-ncs-540 (environment) · cisco-ncs-540-fronthaul (environment) · cisco-ncs-5501 (environment) · cisco-ncs-5501-se (environment) · cisco-ncs-5502 (environment) · cisco-ncs-5502-se (environment) · cisco-ncs-5508 (environment) · cisco-ncs-5516 (environment) · cisco-ncs-560-4 (environment) · cisco-ncs-560-7 (environment) · cisco-ncs-6000 (environment) · cisco-ncs-6008 (environment) · cisco-ios-xrv (same device) · cisco-ios-xrv-9000 (same device)

8101-32Fh · Ciscodevice

80%

All versions

8101-32H · Ciscodevice

80%

All versions

8102-64H · Ciscodevice

80%

All versions

8201 · Ciscodevice

80%

All versions