ADM: Use of Externally-Controlled Format String
CVE-2026-18186 is a high-severity use of externally-controlled format string vulnerability in ADM from Asustor, with a CVSS 3.1 base score of 8.1 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: 5.0.0 through 5.1.3.RI81; 4.1.0 through 4.3.3.RUN1. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.46% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Data Master to 5.1.4.rjv2 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 | 5.0.0 through 5.1.3.RI81; 4.1.0 through 4.3.3.RUN1 | Not stated |
| Asustor | Data Master | 4.1.0.rhu2 through 4.3.3.run1; 5.0.0.ra82 up to, but not including, 5.1.4.rjv2 | 5.1.4.rjv2 |
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
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 7.1 | High | CNA (asustor.com) |
| CVSS 3.1 | 8.1 | High | NVD |
Official description
A stored format string vulnerability was found in the FTP Backup on the ADM. The vulnerability occurs because user-controlled backup configuration data may be written into a task log and later processed through an unsafe format string operation. An authenticated attacker can exploit this issue to disclose memory information or cause denial of service of the affected CGI process. Affected products and versions include: from ADM 4.1.0 through ADM 4.3.3.RUN1 as well as from ADM 5.0.0 through ADM 5.1.3.RI81.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use of Externally-Controlled Format String
The product uses a function that accepts a format string as an argument, but the format string originates from an external source.
How developers prevent this class of flaw
- Choose a language that is not subject to this flaw.
- Ensure that all format string functions are passed a static string which cannot be controlled by the user, and that the proper number of arguments are always sent to that function as well. If at all possible, use functions that do not support the %n operator in format strings.
- Run compilers and linkers with high warning levels, since they may detect incorrect usage.
More Use of Externally-Controlled Format String vulnerabilities (CWE-134)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- 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 Use of Externally-Controlled Format String vulnerabilities
- 8.8 High severity
- 7.8 High severity
- 7.5 High severity
- 8.6 High severity
- 8.1 High severity
- 9.8 Critical severity
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