Executive brief
MikroTik RouterOS, a networking and routing platform used worldwide, accepts improperly formatted RSA signatures in TLS certificate validation and SSH authentication. Because the device trusts a low-exponent root certificate, an attacker can forge trusted certificates for any server without the private key, enabling network traffic interception and credential theft. Additionally, SSH connections can be spoofed to gain unauthorized access to the device.
Technical details
The vulnerability is an improper cryptographic signature verification (CWE-347) affecting RSA/PKCS#1 v1.5 signature validation across TLS/X.509 and SSH protocols. An attacker with network access or control of an outbound TLS connection can exploit the acceptance of malformed signatures combined with a low-exponent (e=3) root CA in the trust store to forge intermediate certificates and issue certificates for arbitrary domains. The same flaw undermines SSH host-key authentication. Fixed in RouterOS 7.23.6 and 7.24.3; versions 7.23.4 and 7.24.2 contained incomplete fixes.
Affected products
- MikroTik RouterOS 7.x before 7.23.6 and 7.24.x before 7.24.3
Timeline
- 2026-09-05: disclosed: Vulnerability disclosed by CERT Polska
- 2026-09-05: exploited: Actively exploited in the wild against RouterOS devices with SSH accessible from the internet