CVE-2026-67278 PUBLISHED

MikroTik RouterOS accepts malformed RSA/PKCS#1 v1.5 signatures during X.509 validation. 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.

This issue was fixed in versions: 6.49.21 (Long-term), 7.23.4 (Long-term) and 7.24.2 (Stable)

• Sławomir Rozbicki (CERT.PL) finder

• 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/6-49-21-long-term-is-released/272802
• https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801
• https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800

• CWE-347 Improper verification of cryptographic signature CWE