Hidden Functionality Enables Remote Telnet Activation via /goform/setSysTools in Nexxt Nebula 300+ (CVE-2026-31847) | HOL Guard CVE

High · CVSS 8.8CVE-2026-31847

Hidden Functionality Enables Remote Telnet Activation via /goform/setSysTools in Nexxt Nebula 300+

Answer in brief

CVE-2026-31847 records a High severity (CVSS 8.8) vulnerability in Hidden Functionality Enables Remote Telnet Activation via /goform/setSysTools in Nexxt Nebula 300+. The current sources do not mark it as known exploited. The current feed maps Nexxt Solutions/Nebula 300+ (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Mar 23, 2026Updated Aug 10, 2026Source checked Sep 24, 2026First seen by HOL Aug 10, 2026Material review Aug 10, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.8
Exploitation: Not marked as known exploited
Affected software: 3 mapped packages or products
Fix availability: Not reported

Why this deserves its current priority

CVSS is 8.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Nexxt Solutions/Nebula 300+ (generic). Check affected ranges and fixed versions before updating.

Affected products and reported versions
Product	Affected versions	Fixed versions
cpe:2.3:h:nexxtsolutions:nebula300plus:-:::::::*	Not reported	Not reported
cpe:2.3:o:nexxtsolutions:nebula300plus_firmware::::::::	Not reported	Not reported

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Nexxt Solutions/Nebula 300+generic	<= 12.01.01.37	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Nexxt Solutions/Nebula 300+.
Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

Published upstream
Mar 23, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 10, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 10, 2026

Sources and claim methodology

Upstream source description

Hidden functionality in the /goform/setSysTools endpoint in Nexxt Solutions Nebula 300+ firmware through version 12.01.01.37 allows remote enablement of a Telnet service. By sending a crafted POST request with parameters such as telnetManageEn=true and telnetPwd, an authenticated attacker can activate a Telnet service on port 23.

Quoted source text, attributed separately from HOL analysis.