CVE-2021-4271Network attack vector

Script execution via unescaped markup attribute values

Published Dec 21, 2022 · Updated Apr 14, 2025

Cross-site scripting in Steven Frank w2wiki allows remote attackers to execute script in a reader's browser through crafted wiki markup. The index.php toHTML function inserts captures from link, image, and message markup directly into HTML attributes without entity encoding. Exploitation requires a reader to view the rendered note; injected script can act in that reader's w2wiki session.

CVSS severity3.5
Low
EPSS probability0.34%
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 Steven Frank w2wiki allows remote attackers to execute script in a reader's browser through crafted wiki markup. The index.php toHTML function inserts captures from link, image, and message markup directly into HTML attributes without entity encoding. Exploitation requires a reader to view the rendered note; injected script can act in that reader's w2wiki session.

The record

CVE
CVE-2021-4271
Published
Dec 21, 2022
Updated
Apr 14, 2025
Vendor
Steven Frank
Product
w2wiki
Classifications
CWE-79, T1203
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

  1. Dec 21, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 14, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesUnavailable in this record.

What is affected?

Steven Frank · w2wikiversion=n/a

Published CVSS scores

3.5VulDBCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
6.1NIST NVDCVSS: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.

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
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

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

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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