ASUSTOR ADM up to 4.3.3.RR42/5.1.2.REO1 VPN Client sscanf stack-based overflow

CVSS Meta Temp Score
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CTI Interest Score
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4.7$0-$5k5.49-

Summaryinfo

A vulnerability classified as critical was found in ASUSTOR ADM up to 4.3.3.RR42/5.1.2.REO1. The impacted element is the function sscanf of the component VPN Client. Executing a manipulation can lead to stack-based overflow. This vulnerability appears as CVE-2026-6643. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability was found in ASUSTOR ADM up to 4.3.3.RR42/5.1.2.REO1. It has been declared as critical. This vulnerability affects the function sscanf of the component VPN Client. The manipulation with an unknown input leads to a stack-based overflow vulnerability. The CWE definition for the vulnerability is 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). As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

A stack-based buffer overflow vulnerability was found in the VPN Clients on the ADM. The issue stems from the use of unbounded sscanf() and passing user-controlled data directly to printf(). Due to the lack of PIE and Stack Canary protections, an authenticated remote attacker can exploit these to execute arbitrary code as the web server user. Affected products and versions include: from ADM 4.1.0 through ADM 4.3.3.RR42 as well as from ADM 5.0.0 through ADM 5.1.2.REO1.

The weakness was presented by Yu-Xiang Huang. The advisory is shared for download at asustor.com. This vulnerability was named CVE-2026-6643 since 04/20/2026. The exploitation appears to be easy. The attack can be initiated remotely. Additional levels of successful authentication are necessary for exploitation. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 04/20/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-23786). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Vendor

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Version

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

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

CVSSv3info

VulDB Meta Base Score: 4.7
VulDB Meta Temp Score: 4.7

VulDB Base Score: 4.7
VulDB Temp Score: 4.7
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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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: 🔒

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Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

04/20/2026 Advisory disclosed
04/20/2026 +0 days CVE reserved
04/20/2026 +0 days VulDB entry created
04/20/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: asustor.com
Researcher: Yu-Xiang Huang
Status: Confirmed

CVE: CVE-2026-6643 (🔒)
GCVE (CVE): GCVE-0-2026-6643
GCVE (VulDB): GCVE-100-358288
EUVD: 🔒

Entryinfo

Created: 04/20/2026 09:36
Updated: 04/20/2026 10:56
Changes: 04/20/2026 09:36 (67), 04/20/2026 10:56 (1)
Complete: 🔍
Cache ID: 216::103

VulDB is the best source for vulnerability data and more expert information about this specific topic.

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