CVE-2021-34763Network attack vector

Script execution via insufficient input validation

Published Oct 27, 2021 · Updated Nov 7, 2024

Cross-site scripting in Cisco Firepower Management Center Software allows remote authenticated users to execute script in a user's browser. The web-based management interface insufficiently validates user-supplied input embedded in a crafted link, causing the browser to run attacker-controlled code in the interface context. Exploitation requires high-privilege FMC credentials and a user who clicks the link; successful attacks can access sensitive browser-based information.

CVSS severity4.8
Medium
EPSS probability0.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Cisco Firepower Management Center Software allows remote authenticated users to execute script in a user's browser. The web-based management interface insufficiently validates user-supplied input embedded in a crafted link, causing the browser to run attacker-controlled code in the interface context. Exploitation requires high-privilege FMC credentials and a user who clicks the link; successful attacks can access sensitive browser-based information.

The record

CVE
CVE-2021-34763
Published
Oct 27, 2021
Updated
Nov 7, 2024
Vendor
ClamAV
Product
Cisco Firepower Management Center
Classifications
CWE-79, T1203
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Oct 27, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 7, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

ClamAV · Cisco Firepower Management Centerversion=n/a

Published CVSS scores

3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/A:N
4.8Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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