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No exploitation reportedFix available

CVE-2021-34718

No exploitation reported by the sources we read.

  • Published2021-09-09
  • Fixed in7.4.1 · 7.3.2
  • WeaknessCWE-88

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2021-09-0905:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-34718?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-34718?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Cisco ios xrversion to verify
BranchAffectedFixed in
7.4≥ 7.4.0, < 7.4.17.4.1
7.3< 7.3.27.3.2

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. Update Cisco ios xr to 7.4.1 · 7.3.2

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • CISA-ADPSSVC decisionnone2024-11-07
  • OpenCVESSVC decisionnone—
  • CNACVSS 3.18.1read 2026-10-23
  • NVDCVSS 3.18.1read 2026-10-23
  • NVDCVSS 2.08.5read 2026-10-23
  • CNAweakness (CWE)CWE-88read 2026-10-23
  • NVDweakness (CWE)CWE-88read 2026-10-23
  • FIRST EPSSEPSS score1.6 %2026-10-23

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Published
2021-09-09
Last Modified
2026-06-17
NVD status
Modified

Frequently asked questions

What is CVE-2021-34718?

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.

Is CVE-2021-34718 actively exploited?

Active exploitation of CVE-2021-34718 has not been confirmed. Its EPSS score was 1.6% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-34718?

CVE-2021-34718 has a CVSS v3 base score of 8.1 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.

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