CVE-2026-86009 Mailu: Domain managers can allow themselves to spoof on other hosted domains they should not control
Domain managers can improperly enable spoofing for domains they do not control, allowing authenticated email forgery.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-86009?
CVE-2026-86009 is a high-severity missing authorization vulnerability in Mailu, published on 16 Oct 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Official description
Mailu is a mail server distributed as a set of Docker images. Prior to f05aeb8322e2f61096af6b089d61ba6f40587d96, domain managers can enable spoofing for hosted domains they do not control. A potentially malicious domain administrator enables spoofing for another hosted domain and can send emails that are authenticated with DKIM/SPF for domains they should not be able to. This vulnerability is addressed by f05aeb8322e2f61096af6b089d61ba6f40587d96.
Which versions are affected by CVE-2026-86009?
How do I fix CVE-2026-86009?
No fix has been published for CVE-2026-86009 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-86009 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-86009 exists.
Sources
Also known as GHSA-crww-m82r-2wfm.