CVE-2026-15937 Agent receiver certificate confusion allows authentication with a certificate issued for another endpoint
Attackers can bypass mTLS authentication in Checkmk by reusing certificates between agents sharing a UUID, allowing unauthorized access to agent receiver endpoints.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-15937?
CVE-2026-15937 is a medium-severity authentication bypass vulnerability in Checkmk, published on 4 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Improper certificate validation in Checkmk <2.5.0p10 allows a relay and a push agent that share the same UUID to reuse each other's mTLS certificate to authenticate against agent receiver endpoints in either direction, because the endpoints do not verify that the certificate was issued by their own root certificate.
Weakness: CWE-295
Which versions are affected by CVE-2026-15937?
How do I fix CVE-2026-15937?
No fix has been published for CVE-2026-15937 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-15937 being exploited?
There is no known exploitation of CVE-2026-15937 in the wild and no public exploit code.
Sources
Also known as GHSA-p53j-vwhv-xp3w.