CVE-2026-67278: TLS server impersonation possible in Mikrotik RouterOS
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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
MikroTik RouterOSto a version that resolves this vulnerability.Fixed in 7.23.6 - Upgrade
Upgrade
MikroTik RouterOSto a version that resolves this vulnerability.Fixed in 7.24.3
Event History
Frequently Asked Questions
Which RouterOS connections are exposed to this attack?
Outbound TLS connections are exposed when an attacker can control or redirect the RouterOS device's connection to the intended server.
Does an attacker need the trusted root CA's private key?
No. The attacker can use the root CA's public certificate to forge a trusted intermediate certificate and issue certificates for arbitrary hostnames.
Which versions contain the fix?
The issue is fixed in RouterOS 6.49.21, 7.23.4, and 7.24.2.