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
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Mikrotik RouterOS
Default version status: unaffected
7.24 to < 7.24.3affected7.0.0 to < 7.23.6affected
References
- https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve ↗
- https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/ ↗
- https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/ ↗
- https://mikrotik.com/supportsec/september-2026-vulnerability/ ↗
- https://forum.mikrotik.com/t/7-23-6-long-term-is-released/273139 ↗
- https://forum.mikrotik.com/t/7-24-3-stable-is-released/273138 ↗