How severe is CVE-2021-41164?

CVE-2021-41164 has a CVSS score of 5.4/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-41164?

CVE-2021-41164 affects the following packages: ckeditor4 (npm). Ecosystems affected: npm.

How do I fix CVE-2021-41164?

Update ckeditor4 to 4.17.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-41164 is resolved across your whole dependency graph.

How do I detect CVE-2021-41164 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ckeditor4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-41164 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2021-41164 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-41164 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-41164?

CVE-2021-41164 has an EPSS (Exploit Prediction Scoring System) score of 1.3%, placing it in the 72th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-41164?

CVE-2021-41164 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2021-41164 published, and has it been updated?

CVE-2021-41164 was published on November 17, 2021 and was last updated on October 24, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

MEDIUM severity

CVE-2021-41164 — ckeditor4

MEDIUM

CVE-2021-41164 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in ckeditor4. A fix is available for ckeditor4 — see the affected versions and patch details below.

Advanced Content Filter (ACF) vulnerability allowing to execute JavaScript code using malformed HTML

Also known asBIT-drupal-2021-41164GHSA-pvmx-g8h5-cprj

Published

Nov 17, 2021

Updated

Oct 24, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs72th percentile — riskier than 72% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

27other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

ckeditor4npm

77Kdownloads / week

Description

Affected packages

The vulnerability has been discovered in the Advanced Content Filter (ACF) module and may affect all plugins used by CKEditor 4.

Impact

A potential vulnerability has been discovered in CKEditor 4 Advanced Content Filter (ACF) core module. The vulnerability allowed to inject malformed HTML bypassing content sanitization, which could result in executing JavaScript code. It affects all users using the CKEditor 4 at version < 4.17.0.

Patches

The problem has been recognized and patched. The fix will be available in version 4.17.0.

For more information

Email us at [email protected] if you have any questions or comments about this advisory.

Acknowledgements

The CKEditor 4 team would like to thank Maurice Dauer (laytonctf) for recognizing and reporting this vulnerability.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`ckeditor4`	all versions	4.17.0`npm install ckeditor4@4.17.0`

Affected Products

10 products · 23 configurations

Application

ckeditorckeditor

≥ 4.0 && < 4.17.0

range

Application

drupaldrupal

≥ 9.2.0 && < 9.2.9

range

fedorafedoraproject

2 versions

3637

Application

agile product lifecycle managementoracle

1 version

9.3.6

Application

application expressoracle

< 22.1

range

Application

banking apisoracle

≥ 18.1 && ≤ 18.3

4 versions

19.119.220.121.1

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ckeditor4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update ckeditor4 to 4.17.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-41164 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

### Affected packages The vulnerability has been discovered in the Advanced Content Filter (ACF) module and may affect all plugins used by CKEditor 4. ### Impact A potential vulnerability has been discovered in CKEditor 4 Advanced Content Filter (ACF) core module. The vulnerability allowed to inject malformed HTML bypassing content sanitization, which could result in executing JavaScript code. It affects all users using the CKEditor 4 at version < 4.17.0. ### Patches The problem has been recognized and patched. The fix will be available in version 4.17.0. ### For more information Email us a

O3 Security · Impact-Aware SCA

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CVSS Score

5.4/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

CWE Classification

CWE-79Cross-site Scripting (XSS)

Weaponization

No Nuclei template, Metasploit module or public proof-of-concept found.

OpenSSF Scorecard

Package health score

ckeditor4

4.2/10

Code-Review0/10

Maintained0/10

Branch-ProtectionN/A

Assessed Nov 2, 2026

Timeline

Disclosed

Nov 17, 2021

Last updated

Oct 24, 2026

Identifiers

CVE-2021-41164

GHSA-pvmx-g8h5-cprj

BIT-drupal-2021-41164

References

Advisorygithub.com · GHSA pvmx g8h5 cprj Advisorydrupal.org · sa core 2021 011 Advisorynvd.nist.gov · CVE 2021 41164 Fixgithub.com · CHANGES.md Fixoracle.com · cpuapr2022 Fixoracle.com · cpujan2022 Weblists.fedoraproject.org · VR76VBN5GW5QUBJFHVXRX36UZ6YTCMW6 Weblists.fedoraproject.org · WOZGMCYDB2OKKULFXZKM6V7JJW4ZZHJP Weboracle.com · cpujul2022 Weblists.fedoraproject.org · VR76VBN5GW5QUBJFHVXRX36UZ6YTCMW6 Weblists.fedoraproject.org · WOZGMCYDB2OKKULFXZKM6V7JJW4ZZHJP Packagegithub.com · ckeditor4

Related vulnerabilities

This CVE is medium severity; 8 of 8 other CVEs affecting ckeditor4 are rated as high or higher (top: high).

CVE-2024-43411CVE-2024-43407CVE-2024-24815CVE-2024-24816CVE-2023-4771CVE-2020-27193CVE-2022-24728CVE-2021-41165

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 24, 2026

CVE-2021-41164 — ckeditor4

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Affected packages

Impact

Patches

For more information

Acknowledgements

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is CVE-2021-41164 in your dependencies?