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CVE-2026-34390 mantisbt CVE debrief

Mantis Bug Tracker (MantisBT) versions 2.28.1 and prior contain a privilege escalation vulnerability in the ProjectUsersAddCommand handler (manage_proj_user_add.php). Users with the manage_project_threshold access level (manager by default) can bypass frontend restrictions and forge a higher access_level value to grant project-level administrator access to any user, including themselves, in projects they manage. The impact is limited: project-level administrator access does not confer global administrative privileges such as managing users, projects, plugins, or custom fields, nor does it allow project deletion. The vulnerability stems from insufficient server-side validation of the access_level parameter. This issue has been resolved in version 2.28.2.

Vendor
mantisbt
Product
Unknown
CVSS
MEDIUM 5.1
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-19
Original CVE updated
2026-07-24
Advisory published
2026-05-19
Advisory updated
2026-07-24

Who should care

MantisBT administrators and security teams managing on-premise or self-hosted MantisBT instances, particularly those with multiple project managers or delegated project administration responsibilities.

Technical summary

The vulnerability exists in manage_proj_user_add.php where the ProjectUsersAddCommand handler fails to properly validate the access_level parameter against the actor's own permissions. While the frontend form restricts selectable access levels, the backend accepts and processes forged higher values. This allows a manager (manage_project_threshold) to escalate any user to project administrator within their managed projects. The fix in 2.28.2 adds server-side enforcement of access level boundaries.

Defensive priority

medium

Recommended defensive actions

  • Upgrade MantisBT to version 2.28.2 or later to remediate this vulnerability.
  • Review project user access levels for any unauthorized elevation that may have occurred prior to patching.
  • Implement principle of least privilege by restricting manage_project_threshold access to only necessary personnel.
  • Monitor access logs for suspicious project user modifications, particularly access_level changes to administrator.
  • Consider implementing additional application-layer access control validation for sensitive operations.

Evidence notes

Vulnerability confirmed through GitHub Security Advisory GHSA-frf7-jhp9-jxm6 and MantisBT bug tracker entries. Fix commit 69e0180f180ed5acf48a8d281a73683a7bf32461 implements additional access control checks. CVSS 4.0 vector: AV:N/AC:L/AT:N/PR:H/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. CWE-284 (Improper Access Control) identified.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-34390 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-34390

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-34390 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-34390

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.