CVE-2021-40541Public exploitNetwork attack vector

Stored script execution via descript filter bypass

Published Oct 11, 2021 · Updated Aug 4, 2024

Stored cross-site scripting in PHPFusion 9.03.110 allows remote authenticated users to execute script in another user's browser. The descript() function's HTML-tag filter fails to neutralize a crafted double-slash suffix, allowing an SVG onload handler to survive filtering. Exploitation requires an authenticated attacker to submit crafted textarea content and another authenticated user or administrator to view it, where the script runs in the viewer's session context.

CVSS severity6.1
Medium
EPSS probability0.57%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored cross-site scripting in PHPFusion 9.03.110 allows remote authenticated users to execute script in another user's browser. The descript() function's HTML-tag filter fails to neutralize a crafted double-slash suffix, allowing an SVG onload handler to survive filtering. Exploitation requires an authenticated attacker to submit crafted textarea content and another authenticated user or administrator to view it, where the script runs in the viewer's session context.

The record

CVE
CVE-2021-40541
Published
Oct 11, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1189
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 11, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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 privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

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

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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