Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-86934 is a critical-severity Authorization Bypass Through User-Controlled Key (CWE-639) vulnerability in Claris Filemaker Server. Its CVSS base score is 9.1 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 24th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-24 (Access Control Decisions) and AC-3 (Access Enforcement) — see the control section below for these in your framework.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-85431
Vulnerability Data
An authorization bypass vulnerability in the FileMaker Server Web Publishing Engine allowed requests containing an extended privilege header to bypass the disabled Custom Web Publishing with XML setting and access the XML Web Publishing interface. This vulnerability is addressed in…
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FileMaker Server version 26.0.3.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Requiring explicit access-control decisions on each request blocks unauthorized key-driven access.
Enforcing approved authorizations on every access request structurally stops a user-controlled key from reaching another user's data.
Least-privilege restrictions limit the scope of data reachable even if a key check is bypassed.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Enforcing authorization policy and least privilege directly blocks user-controlled key tampering that bypasses access checks.
Logical access controls prevent unauthorized data access that results from missing authorization checks on object references.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
A.5.15 directly requires defining and implementing access control rules (including authorization, need-to-know, role-based restrictions, formal requests, and consistency with classification) that stop one user from reaching another's data via a tampered key; the bounded remainder is dynamic or application-specific authorization logic (cross-referenced to 8.26) that may still allow bypass if those downstream rules are flawed.
Managing access rights includes ensuring users can only access their own records and not bypass authorization by altering identifiers.