What is CVE-2026-26987?

### Summary reflected xss via email field ### Details 1. visit `http://127.0.0.1/settings/alerting/email` 2. in the email address input but this payload ` ` 3. notice the alert ### PoC - video attached with the report https://github.com/user-attachments/assets/c1b443f5-85c6-4545-b04f-def06d82b42e ### Impact can lead to ATO

How severe is CVE-2026-26987?

No CVSS score has been assigned to CVE-2026-26987 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-26987?

CVE-2026-26987 affects the following packages: librenms/librenms (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2026-26987?

Update librenms/librenms to 26.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-26987 is resolved across your whole dependency graph.

How do I detect CVE-2026-26987 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-2026-26987 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-2026-26987 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-26987 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-2026-26987?

CVE-2026-26987 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 27th 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-2026-26987?

CVE-2026-26987 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-2026-26987 published, and has it been updated?

CVE-2026-26987 was published on February 20, 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-2026-26987 — librenms

Fix: librenms/librenms@8e626b3

CVE-2026-26987 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 affected by reflected XSS via email field

Also known asGHSA-gqx7-99jw-6fpr

Published

Feb 20, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 12, 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-2026-26987.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs27th percentile — riskier than 27% 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

reflected xss via email field

Details

visit http://127.0.0.1/settings/alerting/email
in the email address input but this payload <img src=1 onerror=alert(document.cookie)>
notice the alert

PoC

video attached with the report https://github.com/user-attachments/assets/c1b443f5-85c6-4545-b04f-def06d82b42e

Impact

can lead to ATO

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`librenms/librenms`	all versions	26.2.0`composer require librenms/librenms:^26.2.0`

Affected Products

1 product · 1 configurations

Application

librenmslibrenms

< 26.2.0

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 26.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-26987 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 reflected xss via email field ### Details 1. visit `http://127.0.0.1/settings/alerting/email` 2. in the email address input but this payload `<img src=1 onerror=alert(document.cookie)>` 3. notice the alert ### PoC - video attached with the report https://github.com/user-attachments/assets/c1b443f5-85c6-4545-b04f-def06d82b42e ### Impact can lead to ATO

O3 Security · Impact-Aware SCA

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