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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Checkmk | Checkmk | 2.4.0 – < 2.4.0p23, 2.3.0 – < 2.3.0p45, 2.2.0 | 2.4.0p23 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | check-mk | No fix yet | — |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 16.04 LTS | check-mk | No fix yet | — |
Advisories 1
- WID-SEC-2026-0681 Checkmk: Schwachstelle ermöglicht Umgehen von Sicherheitsvorkehrungen BSI CERT-Bund (WID) · Mar 24, 2026
References
- https://checkmk.com/werk/18954 vendor-advisory