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CVE-2026-86930 – Process Memory Disclosure (Out-of-Bounds Read) – Claris FileMaker Server for Linux

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Summary

CVE-2026-86930 is a critical out-of-bounds read vulnerability (CWE-125) in Claris FileMaker Server for Linux that allows an unauthenticated, network-based attacker to disclose process memory contents by uploading a maliciously crafted image file to a container field. The flaw is triggered during thumbnail generation in FileMaker WebDirect, and Claris has assigned it a CVSS v3.1 base score of 9.1 (Critical). All FileMaker Server for Linux versions prior to 26.0.3 are affected; the vendor has released 26.0.3 to remediate the issue.

Technical details

  • Root cause: An out-of-bounds read occurs while FileMaker WebDirect generates a thumbnail preview for an image uploaded into a container field. Insufficient bounds checking during image parsing/thumbnail rendering allows the process to read memory outside the intended buffer.
  • Trigger conditions: An attacker uploads a specially crafted image file into any container field accessible through a FileMaker WebDirect-published solution, causing the server to process the image for thumbnail generation.
  • Attack vector: Network-based (AV:N), requires no privileges (PR:N) and no user interaction (UI:N), making it exploitable remotely against any exposed FileMaker WebDirect deployment that accepts container-field uploads.
  • Impact: Successful exploitation discloses process memory contents (high confidentiality impact) and can also affect availability (A:H per the vector string), potentially exposing sensitive in-memory data such as credentials, session tokens, or other secrets handled by the FileMaker Server process; no integrity impact is indicated.

Affected software

  • Claris FileMaker Server for Linux: all versions prior to 26.0.3

Severity

  • CVSS v3.1 Base Score: 9.1 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Mitigation and recommended actions

  • Immediate: Upgrade Claris FileMaker Server for Linux to version 26.0.3 or later, which contains the fix for this vulnerability.
  • If immediate patching is not possible:
    • Restrict or disable public/unauthenticated access to FileMaker WebDirect-published solutions that accept file/image uploads into container fields until the update can be applied.
    • Limit network exposure of FileMaker Server WebDirect endpoints to trusted networks (e.g., via firewall rules or VPN) as a temporary compensating control.
    • Monitor FileMaker Server logs for unusual or repeated container-field upload activity that could indicate exploitation attempts.

References

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