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MEDIUM severity

CVE-2021-39136 — basercms

MEDIUMFix: baserproject/basercms@568d4ca

CVE-2021-39136 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in baserproject/basercms. A fix is available for baserproject/basercms — see the affected versions and patch details below.

Cross-site scripting vulnerability in file upload

Also known asGHSA-hgjr-632x-qpp3
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs59th percentile — riskier than 59% of all scored CVEsHighest risk
0.04%0.50%0.97%1.43%0.5%0.9%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2021-39136 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🐘baserproject/basercms

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

There is a cross-site scripting vulnerability in file upload on the management system of baserCMS.

This is a vulnerability that needs to be addressed when the management system is used by an unspecified number of users. If you are eligible, please update to the new version as soon as possible.

Target

baserCMS 4.5.1 and earlier versions

Vulnerability

Execution of malicious JavaScript code may alter the display of the page or leak cookie information.

Countermeasures

Update to the latest version of baserCMS

Please refer to the next page for details. https://basercms.net/security/JVN_14134801

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistbaserproject/basercmsall versions4.5.1composer require baserproject/basercms:^4.5.1

Affected Products

1 product · 1 configurations
Application
basercmsbasercms
< 4.5.1
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update baserproject/basercms to 4.5.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-39136 is resolved across your whole dependency graph.

  3. 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

There is a cross-site scripting vulnerability in file upload on the management system of baserCMS. This is a vulnerability that needs to be addressed when the management system is used by an unspecified number of users. If you are eligible, please update to the new version as soon as possible. ### Target baserCMS 4.5.1 and earlier versions ### Vulnerability Execution of malicious JavaScript code may alter the display of the page or leak cookie information. ### Countermeasures Update to the latest version of baserCMS Please refer to the next page for details. https://basercms.net/security/
O3 Security · Impact-Aware SCA

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CVE-2021-39136: basercms XSS — Fixed in 4.5.1