QNAP File Station 5 5.5.6.5208 User Account stack-based overflow

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
8.4	$0-$5k	1.91

Summaryinfo

A vulnerability described as critical has been identified in QNAP File Station 5 5.5.6.5208. Affected by this issue is some unknown functionality of the component User Account Handler. The manipulation results in stack-based overflow. This vulnerability is cataloged as CVE-2026-26239. The attack may be launched remotely. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as critical, was found in QNAP File Station 5 5.5.6.5208. Affected is an unknown code block of the component User Account Handler. The manipulation with an unknown input leads to a stack-based overflow vulnerability. CWE is classifying the issue as CWE-121. A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function). This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

A buffer overflow vulnerability has been reported to affect File Station 5. If a remote attacker gains a user account, they can then exploit the vulnerability to modify memory or crash processes. We have already fixed the vulnerability in the following version: File Station 5 5.5.6.5208 and later

The weakness was shared by Moritz Abrell as qsa-26-37. The advisory is available at qnap.com. This vulnerability is traded as CVE-2026-26239 since 02/12/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The technical details are unknown and an exploit is not available.

Upgrading to version 5.5.6.5208 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-35979). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Vendor

QNAP

Name

File Station 5

Version

5.5.6.5208

License

commercial

Website

Vendor: https://www.qnap.com/

CPE 2.3info

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CPE 2.2info

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CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 8.8
VulDB Meta Temp Score: 8.4

VulDB Base Score: 8.8
VulDB Temp Score: 8.4
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AV	AC	Au	C	I	A
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💳	💳	💳	💳	💳	💳
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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Stack-based overflow
CWE: CWE-121 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: File Station 5 5.5.6.5208

Timelineinfo

02/12/2026 CVE reserved
06/10/2026 +117 days Advisory disclosed
06/10/2026 +0 days VulDB entry created
06/10/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: qnap.com

Advisory: qsa-26-37
Researcher: Moritz Abrell
Status: Confirmed

CVE: CVE-2026-26239 (🔒)
GCVE (CVE): GCVE-0-2026-26239
GCVE (VulDB): GCVE-100-370074
EUVD: 🔒

Entryinfo

Created: 06/10/2026 06:49
Updated: 06/10/2026 10:41
Changes: 06/10/2026 06:49 (69), 06/10/2026 10:41 (1)
Complete: 🔍
Cache ID: 216::103

If you want to get best quality of vulnerability data, you may have to visit VulDB.