No exploitation reported

CVE-2021-1435

No exploitation reported by the sources we read.

Published2021-03-24
WeaknessCWE-22

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 web UI of Cisco IOS XE Software could allow an authenticated, remote attacker to inject arbitrary commands that can be executed as the root user. This vulnerability is due to insufficient input validation. An attacker could exploit this vulnerability by sending a crafted request to the web UI of an affected device with arbitrary commands injected into a portion of the request. A successful exploit could allow the attacker to execute arbitrary commands as the root user.

Timeline

dates in UTC

2021-03-2420:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 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-2021-1435?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-1435?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 xe

Branch	Affected	Fixed in	Source
16.9	= 16.9.1	no fix published	NVD
16.9	= 16.9.1a	no fix published	NVD
16.9	= 16.9.1b	no fix published	NVD
16.9	= 16.9.1c	no fix published	NVD
16.9	= 16.9.1d	no fix published	NVD
16.9	= 16.9.1s	no fix published	NVD
16.9	= 16.9.2	no fix published	NVD
16.9	= 16.9.2a	no fix published	NVD
16.9	= 16.9.2s	no fix published	NVD
16.9	= 16.9.3	no fix published	NVD
16.9	= 16.9.3a	no fix published	NVD
16.9	= 16.9.3h	no fix published	NVD

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

Fix

Advisories and patches

tools.cisco.comVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

CISA-ADPSSVC decisionnone2023-11-15
OpenCVESSVC decisionnone—
NVDCVSS 3.17.2read 2026-10-23
CNACVSS 3.06.6read 2026-10-23
NVDCVSS 2.09read 2026-10-23
CNAweakness (CWE)CWE-22read 2026-10-23
FIRST EPSSEPSS score8.5 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Published: 2021-03-24
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-1435?

Is CVE-2021-1435 actively exploited?

Active exploitation of CVE-2021-1435 has not been confirmed. Its EPSS score was 8.5% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-1435?

CVE-2021-1435 has a CVSS v3 base score of 7.2 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H.

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