How severe is CVE-2026-2728?

No CVSS score has been assigned to CVE-2026-2728 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-2728?

CVE-2026-2728 affects the following packages: librenms/librenms (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2026-2728?

Update librenms/librenms to 26.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-2728 is resolved across your whole dependency graph.

How do I detect CVE-2026-2728 in my Packagist dependencies?

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

How do I mitigate CVE-2026-2728 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-2026-2728 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-2728 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-2026-2728?

CVE-2026-2728 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, 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-2026-2728?

CVE-2026-2728 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-2026-2728 published, and has it been updated?

CVE-2026-2728 was published on April 13, 2026 and was last updated on August 12, 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-2026-2728 — librenms/librenms

CVE-2026-2728 is a Cross-site Scripting (XSS) vulnerability in librenms/librenms. A fix is available for librenms/librenms — see the affected versions and patch details below.

LibreNMS: Cross-Site Scripting in ShowConfigController

Also known asGHSA-5gm9-622f-qcg5

Published

Apr 13, 2026

Updated

Aug 12, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 28, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-2728.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

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

🐘librenms/librenms

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

Summary

A Stored Cross-Site Scripting (XSS) vulnerability exists in the ShowConfig page of devices affected by the RANCID Integration settings. The application fails to properly sanitise the rancid_repo_url configuration value. When a user navigates to a device's configuration page, this unsanitised value is rendered directly within an HTML anchor (<a>) tag. This allows an authenticated user with permission to modify external settings to inject malicious JavaScript that will execute in the browser of any user viewing the affected device pages.

Details

The vulnerability is located in the external settings configuration block, specifically at the settings/external/rancid endpoint. When a valid rancid_configs is set, the application renders the corresponding rancid_repo_url as a clickable link labeled "Git Repository" on the /device/{id}/showconfig UI.

Because the rancid_repo_url input is neither validated upon saving nor contextually encoded upon rendering, an attacker can break out of the href attribute context or use JavaScript URIs to attach malicious event handlers or scripts.

This vulnerability is introduced by the line 13 of https://github.com/librenms/librenms/blob/master/includes/html/pages/device/showconfig.inc.php.

PoC

Login as an admin and navigate to /settings/external/rancid.
<img width="790" height="155" alt="image" src="https://github.com/user-attachments/assets/348fff1b-dfce-4735-9273-055113695368" />
Add a valid path to rancid_configs. This can be any directory ended with .git.
Put "></a><img/src/onerror=alert(1)><a x=" into rancid_repo_url config.
<img width="909" height="276" alt="image" src="https://github.com/user-attachments/assets/b8c5d650-ba05-4326-8a2d-bea8defa7373" />
Navigate to a device page and click Config (Or visit /device/{id}/showconfig directly).
The XSS is triggered when visiting the page. It will pop up an alert dialog.
<img width="810" height="454" alt="image" src="https://github.com/user-attachments/assets/4d15784e-ff93-46ec-b13e-08a225a8d6d4" />

Other Payloads

javascript:alert(1)" x=" - triggered by clicking the link.
``" onmouseover="alert(1)" x="` - triggered by hovering on the link

Impact

Since an admin account is required to change the settings, the risk is minimal in systems with a single administrator. However, in environments with multiple administrative users, this constitutes an Admin-to-Admin Cross-Site Scripting attack. It could be used by a compromised admin account to execute arbitrary frontend code in the context of another administrator's session, potentially leading to session hijacking or unauthorized data exposure.

Remediation Advice

Ensure proper sanitisation is performed on affected fields, with all special characters escaped and HTML encoded. This can be done with existing frameworks like HTMLPurifier.

CVE Request

CVE References: https://projectblack.io/blog/librenms-authenticated-rce-and-xss/

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`librenms/librenms`	≥ 25.12.0&&< 26.3.0	26.3.0`composer require librenms/librenms:^26.3.0`

Affected Products

1 product · 1 configurations

Application

librenmslibrenms

< 26.3.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for librenms/librenms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update librenms/librenms to 26.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-2728 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

### Summary A Stored Cross-Site Scripting (XSS) vulnerability exists in the ShowConfig page of devices affected by the RANCID Integration settings. The application fails to properly sanitise the `rancid_repo_url` configuration value. When a user navigates to a device's configuration page, this unsanitised value is rendered directly within an HTML anchor (<a>) tag. This allows an authenticated user with permission to modify external settings to inject malicious JavaScript that will execute in the browser of any user viewing the affected device pages. ### Details The vulnerability is loca

O3 Security · Impact-Aware SCA

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