# CVE-2026-48549: Nagios Core / XI CSRF via cmd.cgi Double-Submit Cookie

> Attackers can bypass CSRF protections in Nagios Core and XI to execute commands as authenticated users, requiring an upgrade to patched versions.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 26 Aug 2026
- **Updated:** 28 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-48549, GHSA-xm5q-p2r5-r5wj, UBUNTU-CVE-2026-48549

## What is CVE-2026-48549?

CVE-2026-48549 is a medium-severity vulnerability in Nagios Core, published on 26 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Nagios Core before 4.5.13 and Nagios XI before 2026R1.5 contains a CSRF vulnerability in cmd.cgi. When no Cookie header is present, the double-submit cookie protection can be bypassed by supplying matching NagFormId and nagFormId values in the POST body, allowing a cross-site request to execute Nagios commands as a currently authenticated user.

Weakness: CWE-352 (Cross-Site Request Forgery)

## Which versions are affected by CVE-2026-48549?


## How do I fix CVE-2026-48549?

Upgrade to a fixed version.

## Is CVE-2026-48549 being exploited?

There is no known exploitation of CVE-2026-48549 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-48549 and fix it if it is affected.

What it is: CVE-2026-48549 is a medium-severity vulnerability in Nagios Core, published on 26 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-48549 in the wild and no public exploit code.

Affected product: Nagios Core. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-48549/ (Markdown: https://insights.sbomify.com/CVE-2026-48549/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-48549
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-48549
- OSV: https://osv.dev/vulnerability/CVE-2026-48549

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-48549/
Summaries are generated and may contain mistakes; the official description above is the record.