# CVE-2026-26239: QNAP File Station 5 stack-based buffer overflow

Source: https://junglewise.ai/threats/cve-2026-26239-qnap-file-station-5-stack-based-buffer-overflow  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-10. Updated: 2026-06-10  
License: CC BY 4.0 with a link back

CVE-2026-26239 · Severity: info · CVSS 8.7 · Published 2026-06-10

A security vulnerability has been identified in QNAP File Station 5, a web-based tool used for managing files on QNAP storage devices. If an attacker obtains access to a standard user account, they can exploit this flaw to crash system processes or modify sensitive memory. This could lead to a total loss of system availability or unauthorized control over the storage device.

Technologies: [QNAP Systems, Inc. File Station 5](https://junglewise.ai/threats/technologies/file-station-5). Vendors: [QNAP Systems, Inc.](https://junglewise.ai/threats/vendors/qnap-systems-inc).

## Quick answers

**Is CVE-2026-26239 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-26239 being exploited in the wild.

**How severe is CVE-2026-26239?** Informational severity, with a CVSS score of 8.7, published 10 June 2026.

**Which products and versions are affected?** QNAP Systems, Inc. File Station 5 versions prior to 5.5.6.5208.

**Is there a fix for CVE-2026-26239?** 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-2026-26239 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-26239?** Check whether you run QNAP Systems or Inc. File Station 5 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 stack-based buffer overflow (CWE-121) exists in QNAP File Station 5. The vulnerability is reachable over the network and requires the attacker to have authenticated access with a standard user account (PR:L). By sending specially crafted input, an attacker can overflow a buffer on the stack to modify memory or crash processes, potentially leading to arbitrary code execution. The issue is resolved in File Station 5 version 5.5.6.5208 and later.

## Affected products

- QNAP Systems, Inc. File Station 5 versions prior to 5.5.6.5208

## Timeline

- 2026-06-10: disclosed
- 2026-06-10: advisory

## References

- [https://www.qnap.com/en/security-advisory/qsa-26-37](https://www.qnap.com/en/security-advisory/qsa-26-37)

## Related threats

- [QNAP File Station 5 buffer overflow](https://junglewise.ai/threats/cve-2026-26241-qnap-file-station-5-buffer-overflow)
- [QNAP File Station 5 stack-based buffer overflow](https://junglewise.ai/threats/cve-2026-26240-qnap-file-station-5-stack-based-buffer-overflow)