ADM: Stack-based Buffer Overflow
CVE-2026-6643 is a critical-severity stack-based buffer overflow vulnerability in ADM from Asustor, with a CVSS 3.1 base score of 9.9 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected ADM versions: 4.1.0 through 4.3.3.RR42; 5.0.0 through 5.1.2.REO1. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.47% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Data Master to 4.3.3.RR42 or 5.1.2.reo1, whichever matches your release line, or a later version.
- Read the advisory on asustor.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| ASUSTOR | ADM | 4.1.0 through 4.3.3.RR42; 5.0.0 through 5.1.2.REO1 | Not stated |
| Asustor | Data Master | 4.1.0.rhu2 up to, but not including, 4.3.3.RR42; 5.0.0.ra82 up to, but not including, 5.1.2.reo1 | 4.3.3.RR42, 5.1.2.reo1 |
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
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- 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:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.6 | High | CNA (asustor.com) |
| CVSS 3.1 | 9.9 | Critical | NVD |
Official 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Stack-based Buffer Overflow
The product writes past the end of a buffer that was allocated on the stack.
How developers prevent this class of flaw
- 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.
- Use an abstraction library to abstract away risky APIs. Not a complete solution.
- Implement and perform bounds checking on input.
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 ADM
- 9.2 Critical severity
- 8.8 High severity
- 8.1 High severity
- 7.2 High severity
- 8.1 High severity
- 8.1 High severity
Recent Stack-based Buffer Overflow vulnerabilities
- 8.8 High severity
- 8.6 High severity
- 7.5 High severity
- 9.8 Critical severity
- 8.7 High severity
- 7.5 High severity
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