CVE-2026-34390

CVE-2026-34390 is a medium-severity vulnerability with a CVSS 4.0 base score of 5.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-284.

Key facts

Description

Mantis Bug Tracker (MantisBT) is an open source issue tracker. Versions 2.28.1 and prior have a Privilege Escalation vulnerability where insufficient access control checks in ProjectUsersAddCommand (manage_proj_user_add.php) allow users having manage_project_threshold access level (manager by default) to grant project-level administrator access to any user (including themselves) in any Project they have manager rights in. The normal project-user add form restricts the selectable access levels to the actor's own project role or below. However, the backend handler still accepts a forged higher access_level value and writes it. The consequences of the privilege escalation are slight, as having administrator access at Project level is effectively not very different from being manager, and it does not actually give administrator privileges on the whole MantisBT instance. In particular, it does not let the upgraded user delete the Project or grant them any access to global administrative functions such as managing Users, Projects, Plugins, Custom Fields, etc. This issue has been fixed in version 2.28.2.

Frequently asked questions

What is CVE-2026-34390?
Mantis Bug Tracker (MantisBT) is an open source issue tracker. Versions 2.28.1 and prior have a Privilege Escalation vulnerability where insufficient access control checks in ProjectUsersAddCommand (manage_proj_user_add.php) allow users having manage_project_threshold access level (manager by default) to grant project-level administrator access to any user (including themselves) in any Project they have manager rights in. The normal project-user add form restricts the selectable access levels to the actor's own project role or below. However, the backend handler still accepts a forged higher access_level value and writes it. The consequences of the privilege escalation are slight, as having administrator access at Project level is effectively not very different from being manager, and it does not actually give administrator privileges on the whole MantisBT instance. In particular, it does not let the upgraded user delete the Project or grant them any access to global administrative functions such as managing Users, Projects, Plugins, Custom Fields, etc. This issue has been fixed in version 2.28.2.
How severe is CVE-2026-34390?
CVE-2026-34390 has a CVSS 4.0 base score of 5.1, rated medium severity.
Is CVE-2026-34390 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (34th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-34390?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-34390 have an EU (EUVD) identifier?
Yes. CVE-2026-34390 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30994.
When was CVE-2026-34390 published?
CVE-2026-34390 was published on 2026-05-19 and last updated on 2026-06-17.

References

Other CWE-284 (Improper Access Control) vulnerabilities

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