CVE-2021-1490Network attack vector

Unauthenticated XSS via unvalidated upload

Published May 6, 2021 · Updated Nov 8, 2024

Cross-site scripting in Cisco Secure Web Appliance allows unauthenticated remote attackers to execute script in a user's web management interface. The web management interface improperly validates user-supplied input in a crafted file that a user is persuaded to retrieve and upload, allowing the payload to run in the affected interface. Exploitation requires convincing a user to handle the malicious file; successful attacks can access browser-based information or alter interface actions, but do not inherently interrupt appliance availability.

CVSS severity6.1
Medium
EPSS probability0.70%
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 Secure Web Appliance allows unauthenticated remote attackers to execute script in a user's web management interface. The web management interface improperly validates user-supplied input in a crafted file that a user is persuaded to retrieve and upload, allowing the payload to run in the affected interface. Exploitation requires convincing a user to handle the malicious file; successful attacks can access browser-based information or alter interface actions, but do not inherently interrupt appliance availability.

The record

CVE
CVE-2021-1490
Published
May 6, 2021
Updated
Nov 8, 2024
Vendor
ClamAV
Product
Cisco Secure Web Appliance
Classifications
CWE-79, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 8, 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 privilegesunauthenticated

What is affected?

ClamAV · Cisco Secure Web Applianceversion=n/a

Published CVSS scores

4.7Cisco Systems, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N
6.1NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3NVDAV:N/AC:M/Au:N/C:N/I:P/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1189Drive-by Compromise

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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