CVE-2021-39420Public exploitNetwork attack vector

Browser script execution via reflected request parameters

Published Nov 8, 2021 · Updated Aug 4, 2024

Cross-site scripting in VFront 0.99.5 allows remote attackers to execute script in a user's browser via crafted request URLs. The search_all.php and add.attach.php endpoints place the s and msg request parameters into generated pages without neutralizing script syntax. Exploitation requires a user to follow a crafted URL; the add.attach.php path also requires t to name an existing managed database table.

CVSS severity6.1
Medium
EPSS probability0.66%
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 VFront 0.99.5 allows remote attackers to execute script in a user's browser via crafted request URLs. The search_all.php and add.attach.php endpoints place the s and msg request parameters into generated pages without neutralizing script syntax. Exploitation requires a user to follow a crafted URL; the add.attach.php path also requires t to name an existing managed database table.

The record

CVE
CVE-2021-39420
Published
Nov 8, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 8, 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 privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.3NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1NVDCVSS:3.1/AV:N/AC:L/PR:N/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.

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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
Privilegesunauthenticated
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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