How severe is CVE-2026-6643?

CVE-2026-6643 has a CVSS 3.x base score of 9.9, rated critical severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-6643 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-6643?

CVE-2026-6643 affects Asustor Data Master. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-6643?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-6643 have an EU (EUVD) identifier?

Yes. CVE-2026-6643 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-23786.

When was CVE-2026-6643 published?

CVE-2026-6643 was published on 2026-04-20 and last updated on 2026-06-17.

CVE-2026-6643

CVE-2026-6643 is a critical-severity vulnerability in Asustor Data Master with a CVSS 3.x base score of 9.9. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-121.

Key facts

Severity: Critical (CVSS 3.x base score 9.9)
CVSS v4: 8.6
EPSS exploit prediction: 0% (37th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-23786
Weakness: CWE-121
Affected product: Asustor Data Master
Published: 2026-04-20
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2026-6643?: 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.
How severe is CVE-2026-6643?: CVE-2026-6643 has a CVSS 3.x base score of 9.9, rated critical severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-6643 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-6643?: CVE-2026-6643 affects Asustor Data Master. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-6643?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-6643 have an EU (EUVD) identifier?: Yes. CVE-2026-6643 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-23786.
When was CVE-2026-6643 published?: CVE-2026-6643 was published on 2026-04-20 and last updated on 2026-06-17.

References

https://www.asustor.com/security/security_advisory_detail?id=54

Affected products (1)

cpe:2.3:o:asustor:data_master:*:*:*:*:*:*:*:*

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