# CVE-2026-81855 — Wärtsilä FOS-Onboard

> As of 2026-09-15, CVE-2026-81855 is a CRITICAL-severity vulnerability in Wärtsilä FOS-Onboard, CVSS v3.1 9.1, EPSS 0.4% (40.6th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-81855 as of 2026-09-15; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-09-15

## What is CVE-2026-81855?

A hardcoded cryptographic client authentication key vulnerability exists in the robot testing framework component of Wärtsilä FOS-Onboard.

The record classifies CVE-2026-81855 under weakness class [CWE-321](https://intel.threadlinqs.com/cwe/CWE-321). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 20 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 9.1 — CRITICAL (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **CVSS v4.0 base score:** 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **EPSS (FIRST):** 0.4% probability of exploitation in the next 30 days, higher than 40.6% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 6.2/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-09-15

## Is CVE-2026-81855 being exploited?

It currently carries a trending score of 40 in the Threadlinqs vulnerability feed.

## Affected products and versions

- **Wärtsilä**: FOS-Onboard

## How to fix CVE-2026-81855

No vendor patch reference has been recorded for CVE-2026-81855 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-81855

No threat campaign in the Threadlinqs corpus currently references CVE-2026-81855, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on 2026-09-16. This product uses the NVD API but is not endorsed or certified by the NVD.

**Other references**

- [wartsila.com](https://www.wartsila.com/services-catalogue/engine-services-4-stroke/wartsila-ics-patch-deployment#contact)
- [cisa.gov](https://www.cisa.gov/news-events/ics-advisories/icsa-26-258-02)
- [github.com](https://github.com/cisagov/CSAF/blob/develop/csaf_files/OT/white/2026/icsa-26-258-02.json)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-81855
Full detection coverage and IOCs for threats exploiting CVE-2026-81855 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp