CVE-2021-38156
CVE-2021-38156 is a Cross-site Scripting (XSS) vulnerability. 1 public exploit reference exists, so weaponization risk is real. No vendor fix is recorded yet; mitigation options are listed below.
In Nagios XI before 5.8.6, XSS exists in the dashboard page (/dashboards/#) when administrative users attempt to edit a dashboard.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Description
In Nagios XI before 5.8.6, XSS exists in the dashboard page (/dashboards/#) when administrative users attempt to edit a dashboard.
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
No patched version of the affected component has shipped for CVE-2021-38156 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2021-38156 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-38156. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
How to detect CVE-2021-38156
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2021-38156 -u https://target- Template
- Nagios XI < 5.8.6 - Cross-Site Scripting
- Severity
- medium
- Impact
- Authenticated attackers can inject malicious JavaScript via XSS in the dashboard title field, potentially stealing administrator session cookies or performing administrative actions.
- Remediation
- Upgrade to Nagios XI version 5.8.6 or later.
Template by ProjectDiscovery nuclei-templates (ritikchaddha), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2021-38156 in your dependencies?
O3 Security finds CVE-2021-38156 across dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.