FileMaker Server: Heap-based Buffer Overflow
CVE-2026-86926 is a high-severity heap-based buffer overflow vulnerability in FileMaker Server from Claris, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists version 26.0.3 as the first without the flaw, so updating FileMaker Server to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.13% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update FileMaker Server to 26.0.3 or a later version.
- Read the advisory on support.claris.com for workarounds and exact fixed builds.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Claris | FileMaker Server | before 26.0.3 | 26.0.3 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. Scored by CISA (ADP).
Official description
A heap buffer overflow vulnerability in the FileMaker Server database engine block parsing routine allowed a maliciously crafted .fmp12 database file to cause memory corruption, potentially leading to arbitrary code execution. This vulnerability is addressed in FileMaker Server version 26.0.3.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Heap-based Buffer Overflow
The product writes past the end of a buffer that was allocated on the heap.
How developers prevent this class of flaw
- Pre-design: Use a language or compiler that performs automatic bounds checking.
- Use an abstraction library to abstract away risky APIs. Not a complete solution.
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other vulnerabilities in FileMaker Server
- 9.1 Critical severity
- 9.1 Critical severity
- 9.8 Critical severity
- 7.5 High severity
Recent Heap-based Buffer Overflow vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 8.3 High severity
- 9.8 Critical severity
F5 BIG-IP APM Heap-based Buffer Overflow Exploited
- 8.0 High severity
- 7.8 High severity
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