CVE-2021-41258Network attack vector

Stored XSS via unescaped image block fields

Published Nov 16, 2021 · Updated Aug 4, 2024

Stored XSS in Content Folder Kirby 3.5.0 through 3.5.7.1 allows remote authenticated users to execute JavaScript in visitors' browsers. The default config/blocks/image/image.php snippet outputs attacker-controlled source, alt, and link values without HTML escaping. Exploitation requires an authenticated Panel user and a site using the blocks field with the default image snippet; rendered content can act with a visiting user's browser session.

CVSS severity5.4
Medium
EPSS probability0.81%
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 Content Folder Kirby 3.5.0 through 3.5.7.1 allows remote authenticated users to execute JavaScript in visitors' browsers. The default config/blocks/image/image.php snippet outputs attacker-controlled source, alt, and link values without HTML escaping. Exploitation requires an authenticated Panel user and a site using the blocks field with the default image snippet; rendered content can act with a visiting user's browser session.

The record

CVE
CVE-2021-41258
Published
Nov 16, 2021
Updated
Aug 4, 2024
Vendor
Content Folder
Product
Kirby
Classifications
CWE-80, T1189
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 16, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 3.5.0, < 3.5.8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Content Folder · Kirbyversion=>= 3.5.0, < 3.5.8

Published CVSS scores

2.1NVDAV:N/AC:H/Au:S/C:N/I:P/A:N
5.4GitHubCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
5.4NVDCVSS: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 exploitUnconfirmed

Weakness, pattern, technique

CWE-80Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)
T1189Drive-by Compromise

Public exploit references

No public exploit references are available in this record.

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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