CVE-2021-34718

Cisco IOS XR Software Arbitrary File Read and Write Vulnerability

HIGH

8.1

CVSS Score

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

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

36 products affected across 1 vendorIOS XrAsr 9010Asr 9904

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Severity

HIGH8.1

Exploit prediction

EPSS 2%

SSVC

No known exploit

Description

A vulnerability in the SSH Server process of Cisco IOS XR Software could allow an authenticated, remote attacker to overwrite and read arbitrary files on the local device. This vulnerability is due to insufficient input validation of arguments that are supplied by the user for a specific file transfer method. An attacker with lower-level privileges could exploit this vulnerability by specifying Secure Copy Protocol (SCP) parameters when authenticating to a device. A successful exploit could allow the attacker to elevate their privileges and retrieve and upload files on a device that they should not have access to.

Affected

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

IOS Xr · Cisco

95%

v < 7.3.27.4.0 ≤ v < 7.4.1

Affected range stops below 7.3.2, so it looks safe — our inference, not a vendor statement

Affected range stops below 7.4.1, so it looks safe — our inference, not a vendor statement

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)

Asr 9000V-V2 · Ciscodevice

80%

All versions

Asr 9001 · Ciscodevice

80%

All versions

Asr 9006 · Ciscodevice

80%

All versions

Asr 9010 · Ciscodevice

80%

All versions