How severe is CVE-2026-30879?

No CVSS score has been assigned to CVE-2026-30879 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-30879?

CVE-2026-30879 affects the following packages: baserproject/basercms (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2026-30879?

Update baserproject/basercms to 5.2.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-30879 is resolved across your whole dependency graph.

How do I detect CVE-2026-30879 in my Packagist dependencies?

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.

How do I mitigate CVE-2026-30879 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-2026-30879 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-30879 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-2026-30879?

CVE-2026-30879 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 15th 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-2026-30879?

CVE-2026-30879 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-2026-30879 published, and has it been updated?

CVE-2026-30879 was published on March 31, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘 Packagist

Not in CISA KEV

CVE-2026-30879 — basercms

CVE-2026-30879 is a Cross-site Scripting (XSS) vulnerability in baserproject/basercms. A fix is available for baserproject/basercms — see the affected versions and patch details below.

baserCMS: Cross-site scripting vulnerability in blog post

Also known asGHSA-jmq3-x8q7-j9qm

Published

Mar 31, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 29, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-30879.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk-0.08%

Lower risk than most CVEs15th percentile — riskier than 15% of all scored CVEsHighest risk

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

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

baserCMS has a cross-site scripting vulnerability in blog posts.

Target

baserCMS 5.2.1 and earlier versions

Vulnerability

Malicious Javascript may be executed in blog posts.

Countermeasures

Update to the latest version of baserCMS

Please refer to the following page to reference for more information. https://basercms.net/security/JVN_20837860

Credits

Gai Tanaka@Mitsui Bussan Secure Directions, Inc.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`baserproject/basercms`	all versions	5.2.3`composer require baserproject/basercms:^5.2.3`

Affected Products

1 product · 1 configurations

Application

basercmsbasercms

< 5.2.3

range

Detection & mitigation playbook

Open-source dependency

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.
Fix
Update baserproject/basercms to 5.2.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-30879 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

baserCMS has a cross-site scripting vulnerability in blog posts. ### Target baserCMS 5.2.1 and earlier versions ### Vulnerability Malicious Javascript may be executed in blog posts. ### Countermeasures Update to the latest version of baserCMS Please refer to the following page to reference for more information. https://basercms.net/security/JVN_20837860 ### Credits Gai Tanaka@Mitsui Bussan Secure Directions, Inc.

O3 Security · Impact-Aware SCA

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