# CVE-2026-86926: Claris FileMaker Server heap buffer overflow in database block parsing

Source: https://junglewise.ai/threats/cve-2026-86926-a-heap-buffer-overflow-vulnerability-in-the-filemaker-server  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-23. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-86926 · Severity: high · CVSS 7.8 · Published 2026-09-23

FileMaker Server is a database platform used for storing and managing critical business data. A flaw in how it processes database files allows an attacker to craft a malicious .fmp12 file that, when opened, corrupts memory and could lead to running arbitrary code on the server hosting the database.

Technologies: [Claris FileMaker Server](https://junglewise.ai/threats/technologies/filemaker-server). Vendors: [Claris](https://junglewise.ai/threats/vendors/claris).

## Quick answers

**Is CVE-2026-86926 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-86926 being exploited in the wild.

**How severe is CVE-2026-86926?** High severity, with a CVSS score of 7.8, published 23 September 2026.

**Which products and versions are affected?** Claris FileMaker Server before 26.0.3.

**Is there a fix for CVE-2026-86926?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-86926 attacked?** It is attacked with local access, in a web application.

**Am I affected by CVE-2026-86926?** Check whether you run Claris FileMaker Server at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A heap buffer overflow exists in the FileMaker Server database engine's block parsing routine when processing .fmp12 files. An attacker can supply a maliciously crafted database file to trigger the overflow, leading to memory corruption and potential arbitrary code execution. The vulnerability is fixed in FileMaker Server 26.0.3.

## Affected products

- Claris FileMaker Server before 26.0.3

## Timeline

- 2026-09-23: disclosed

## References

- [https://support.claris.com/s/answerview?anum=000049219&language=en_US](https://support.claris.com/s/answerview?anum=000049219&language=en_US)

## Related threats

- [FileMaker Server authorization bypass in Web Publishing Engine](https://junglewise.ai/threats/cve-2026-86934-an-authorization-bypass-vulnerability-in-the-filemaker-server-web)
- [FileMaker Server out-of-bounds read in image processing](https://junglewise.ai/threats/cve-2026-86930-an-out-of-bounds-read-vulnerability-in-filemaker-server-for-linux)
- [Claris FileMaker Server code execution in Open Source LLM setup](https://junglewise.ai/threats/cve-2026-43752-claris-filemaker-server-code-execution-in-open-source-llm-setup)