MicroServer: Command Shell in Externally Accessible Directory
CVE-2025-66620 is a high-severity command shell in externally accessible directory vulnerability in MicroServer from Columbia Weather Systems, with a CVSS 3.1 base score of 7.2 out of 10. It can be exploited remotely over the network by an attacker with administrator privileges, without any action from a user. The record lists version MS_4.1_14142 as the first without the flaw, so updating MicroServer to that release or later removes the exposure. 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 MicroServer to MS_4.1_14142 or a later version.
- Update Weather Microserver Firmware to MS_4.1_14142 or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Columbia Weather Systems | MicroServer | before MS_4.1_14142 | MS_4.1_14142 |
| Columbiaweather | Weather Microserver Firmware | before MS_4.1_14142 | MS_4.1_14142 |
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
- HighAdministrator-level access is required first.
- 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
- 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:H/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.6 | High | CNA (hq.dhs.gov) |
| CVSS 3.1 | 8.0 | High | CNA (hq.dhs.gov) |
| CVSS 3.1 | 7.2 | High | NVD |
Official description
An unused webshell in MicroServer allows unlimited login attempts, with sudo rights on certain files and directories. An attacker with admin access to MicroServer can gain limited shell access, enabling persistence through reverse shells, and the ability to modify or remove data stored in the file system.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Command Shell in Externally Accessible Directory
A possible shell file exists in /cgi-bin/ or other accessible directories. This is extremely dangerous and can be used by an attacker to execute commands on the web server.
How developers prevent this class of flaw
- Remove any Shells accessible under the web root folder and children directories.
More Command Shell in Externally Accessible Directory vulnerabilities (CWE-553)
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
Third-party and government advisories
- github.com/cisagov/CSAF/blob/develop/csaf_files/OT/white/2026/icsa-26-006-01.jsonThird Party Advisory
- cisa.gov/news-events/ics-advisories/icsa-26-006-01Third Party Advisory, US Government Resource
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