MikroTik RouterOS Improper Verification of Cryptographic Signature (CVE-2026-67278)

critical Tenable OT Security Plugin ID 506061

Synopsis

The remote OT asset is affected by a vulnerability.

Description

MikroTik RouterOS accepts malformed RSA/PKCS#1 v1.5 signatures across RSA-based services, including TLS/X.509 certificate validation and SSH host-key authentication. Because its trust store includes an e=3 root CA, an attacker controlling or redirecting an outbound RouterOS TLS connection can use the root's public certificate - without its private key - to forge a trusted intermediate and issue certificates for arbitrary hostnames, enabling TLS server impersonation. The same permissive verification also undermines RSA-based SSH authentication.
This issue affects only 7.x branch was fixed in versions: 7.23.6 (Long-term) and 7.24.3 (Stable). Releases 7.23.4 and 7.24.2 included an incomplete fix.

This plugin only works with Tenable.ot.
Please visit https://www.tenable.com/products/tenable-ot for more information.

Solution

Refer to the vendor advisory.

Plugin Details

Severity: Critical

ID: 506061

File Name: tenable_ot_mikrotik_CVE-2026-67278.nasl

Version: 1.1

Type: Remote

Family: Tenable.ot

Published: 10/5/2026

Updated: 10/5/2026

Supported Sensors: Tenable OT Security

Risk Information

VPR

Risk Factor: Medium

Score: 4.3

Percentile: 53.43

CVSS v3

Risk Factor: Critical

Base Score: 9.1

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Vulnerability Information

CPE: cpe:/o:mikrotik:routeros:7

Required KB Items: Tenable.ot/MikroTik

Patch Publication Date: 9/5/2026

Vulnerability Publication Date: 9/5/2026

Reference Information

CVE: CVE-2026-67278

CWE: 347

Detections

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