CVE-2021-3243Public exploitNetwork attack vector

Host command execution via poisoned activity logs

Published Apr 15, 2021 · Updated Aug 3, 2024

Stored XSS in Wfilter ICF 5.0.117 allows remote attackers on the same LAN to execute script in an administrator's browser. The web-activity history view inserts captured User-Agent values into the page without neutralizing script, and injected JavaScript can submit a request to runDll, which loads an attacker-chosen DLL and exported function. Exploitation requires Wfilter to record the crafted traffic and an administrator to open the history view; the demonstrated chain uses WinExec for command execution on the host.

CVSS severity6.1
Medium
EPSS probability0.73%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in Wfilter ICF 5.0.117 allows remote attackers on the same LAN to execute script in an administrator's browser. The web-activity history view inserts captured User-Agent values into the page without neutralizing script, and injected JavaScript can submit a request to runDll, which loads an attacker-chosen DLL and exported function. Exploitation requires Wfilter to record the crafted traffic and an administrator to open the history view; the demonstrated chain uses WinExec for command execution on the host.

The record

CVE
CVE-2021-3243
Published
Apr 15, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

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 exploitPublished

Weakness, pattern, technique

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

Public exploit references

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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