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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mikrotik | RouterOS | 7.24 – < 7.24.3, 7.0.0 – < 7.23.6 | 7.24.3 |
Advisories 1
- WID-SEC-2026-3193 MikroTik RouterOS: Mehrere Schwachstellen BSI CERT-Bund (WID) · Sep 10, 2026
References
- https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve third-party-advisory
- https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/ technical-description
- https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/ exploit
- https://mikrotik.com/supportsec/september-2026-vulnerability/ vendor-advisory
- https://forum.mikrotik.com/t/7-23-6-long-term-is-released/273139 release-notes
- https://forum.mikrotik.com/t/7-24-3-stable-is-released/273138 release-notes