# CVE-2026-48551: Nagios Core / XI CSRF Protection Bypass via Double-Submit Cookie

> Attackers can bypass CSRF protection to execute commands as authorized users via malicious links in Nagios Core and XI.

- **Severity:** Medium 6.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:N/SI:H/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:** 12 Aug 2026
- **Updated:** 14 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-48551, GHSA-4f3c-j3m4-8h7h, UBUNTU-CVE-2026-48551

## What is CVE-2026-48551?

CVE-2026-48551 is a medium-severity vulnerability in Nagios Core, published on 12 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 4.5.14 and Nagios XI before 2026R1.7 contain a cross-site request forgery protection bypass via a self-supplied double-submit cookie. An attacker can supply matching cookie and request parameter values to bypass CSRF protection, enabling unauthenticated attackers to run commands as authorized users via malicious links.

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

## Which versions are affected by CVE-2026-48551?


## How do I fix CVE-2026-48551?

Upgrade to a fixed version.

## Is CVE-2026-48551 being exploited?

There is no known exploitation of CVE-2026-48551 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-48551 and fix it if it is affected.

What it is: CVE-2026-48551 is a medium-severity vulnerability in Nagios Core, published on 12 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-2026-48551 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-2026-48551/ (Markdown: https://insights.sbomify.com/CVE-2026-48551/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-48551
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-48551
- OSV: https://osv.dev/vulnerability/CVE-2026-48551

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-48551/
Summaries are generated and may contain mistakes; the official description above is the record.