CVE-2026-19872Network attack vector

Cross-site scripting via unescaped validation errors

Published Sep 8, 2026 · Updated Sep 8, 2026

Cross-site scripting in HTML::FormHandler before 0.410000 allows remote attackers to run script via rejected form values. Library wrappers and renderers interpolate no_match, not_allowed, and type-constraint error strings containing submitted values directly into HTML without escaping. A check regexp, check list, or type constraint is sufficient; exposure requires the library's rendering roles, and successful injection runs in the victim application's origin.

CVSS severity6.1
Medium
EPSS probability0.33%
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 HTML::FormHandler before 0.410000 allows remote attackers to run script via rejected form values. Library wrappers and renderers interpolate no_match, not_allowed, and type-constraint error strings containing submitted values directly into HTML without escaping. A check regexp, check list, or type constraint is sufficient; exposure requires the library's rendering roles, and successful injection runs in the victim application's origin.

The record

CVE
CVE-2026-19872
Published
Sep 8, 2026
Updated
Sep 8, 2026
Vendor
FormHandler Contributors
Product
HTML-FormHandler
Classifications
CWE-79
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 8, 2026Record 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=0 <0.410000

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

FormHandler Contributors · HTML-FormHandlerversion=0 <0.410000

Published CVSS scores

6.1TenableCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3TenableAV: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.

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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 exploitUnconfirmed

Weakness, pattern, technique

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

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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