EXPOSURES › CVE-2026-67278
CVE-2026-67278
CRITICALMikroTik RouterOS accepts malformed RSA/PKCS#1 v1.5 signatures, enabling TLS impersonation and undermining SSH authentication.
An attacker can forge trusted intermediate certificates using the public root CA certificate without the private key, allowing TLS server impersonation and compromising SSH host-key authentication. DIB organizations must ensure RouterOS is patched to versions 7.23.6 or 7.24.3, as incomplete fixes in 7.23.4 and 7.24.2 left systems vulnerable. This failure impacts compliance by exposing network infrastructure to man-in-the-middle attacks and unauthorized access.
Shame score — The vulnerability allows TLS impersonation and undermines SSH authentication, which are critical for securing network communications and remote access, and the incomplete fixes in earlier versions show a lack of thorough patching.
▸ RECOMMENDED ACTION Critical severity — schedule patching of the affected products.
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.