CVE-2026-8406 openSIS Classic 9.3 - Insecure Direct Object Reference in Sent Mail
Authenticated users can read other users' sent messages by manipulating the mail_id parameter in the messaging module.
- 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-2026-8406?
CVE-2026-8406 is a high-severity missing authorization vulnerability in OS4ED openSIS-Classic, published on 11 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
openSIS Classic 9.3 contains an insecure direct object reference vulnerability in the messaging module. Any authenticated user with access to the messaging module can request sent-message details from modules/messaging/SentMail.php by supplying an arbitrary mail_id value.
Weakness: CWE-639
Which versions are affected by CVE-2026-8406?
How do I fix CVE-2026-8406?
No fix has been published for CVE-2026-8406 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-2026-8406 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-8406 exists.
Sources
Also known as GHSA-vgf3-fpxc-h968.