CVE-2026-67278: MikroTik RouterOS

Critical severity, CVSS 9.1. EPSS: 0.3% chance of exploitation in the next 30 days.

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.

Affected products

• MikroTik RouterOS: from 7.0, before 7.23.6 (fixed in 7.23.6); from 7.24, before 7.24.3 (fixed in 7.24.3)

Published 2026-09-05. Last modified 2026-09-25.