# CVE-2026-84411 — MikroTik RouterOS

> As of 2026-10-03, CVE-2026-84411 is a CRITICAL-severity vulnerability in MikroTik RouterOS, CVSS v3.1 9.8, EPSS 0.9% (59.9th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-84411, most recently “Critical MikroTik RouterOS Integer Underflow Vulnerability (CVE-2026-84411) Enables Unauthenticated Remote Code Execution”.

**Last updated:** 2026-10-03

## What is CVE-2026-84411?

The web management service in affected RouterOS versions contains an integer underflow in its HTTP request body handling that is reachable before authentication. This can be leveraged by an unauthenticated network attacker to achieve arbitrary code execution as root, or to cause a denial of service, using a single crafted request.

The record classifies CVE-2026-84411 under weakness class [CWE-191](https://cwe.mitre.org/data/definitions/191.html). 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, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 21 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 9.8 — CRITICAL (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **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:H/SC:N/SI:N/SA:N`)
- **EPSS (FIRST):** 0.9% probability of exploitation in the next 30 days, higher than 59.9% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 7.3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-10-02, last modified 2026-10-03

## Is CVE-2026-84411 being exploited?

It currently carries a trending score of 48 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [MikroTik](https://intel.threadlinqs.com/vendors/mikrotik): RouterOS

## How to fix CVE-2026-84411

No vendor patch reference has been recorded for CVE-2026-84411 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-2026-84411

1 tracked threat in the Threadlinqs corpus references CVE-2026-84411, either in the campaign’s CVE list or as an indicator on the campaign record.

- [Critical MikroTik RouterOS Integer Underflow Vulnerability (CVE-2026-84411) Enables Unauthenticated Remote Code Execution](https://intel.threadlinqs.com/threat/TL-2026-2805) — CRITICAL · 2026-09-30

## Sources

Enriched from CVE.org, FIRST EPSS. Last verified by Threadlinqs on 2026-10-10.

**Other references**

- [mikrotik.com](https://mikrotik.com/download)
- [cisa.gov](https://www.cisa.gov/news-events/ics-advisories/icsa-26-272-06)
- [github.com](https://github.com/cisagov/CSAF/blob/develop/csaf_files/OT/white/2026/icsa-26-272-06.json)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-84411
Full detection coverage and IOCs for threats exploiting CVE-2026-84411 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp