CVE-2026-67276: CWE-347 Improper verification of cryptographic signature in Mikrotik RouterOS

RouterOS versions in the 7.x branch prior to 7.23.4 and 7.24.2 do not fully verify RSA public keys during SSH authentication. Specifically, the verification process checks the key type and modulus but omits the exponent. Because the signature verification uses the client-supplied key, an attacker who knows an authorized RSA modulus can supply a key with exponent one, forge a valid signature, and open an SSH command channel as the target user without needing the private key. This cryptographic signature verification flaw is tracked as CWE-347.

An attacker can bypass SSH authentication by forging signatures using a known RSA modulus and an exponent of one, allowing unauthorized SSH command channel access as any user with an authorized RSA key. This compromises the confidentiality and integrity of the affected RouterOS devices, potentially leading to full system compromise.

Upgrade affected Mikrotik RouterOS 7.x versions to 7.23.4 (Long-term) or 7.24.2 (Stable) or later, where this vulnerability is fixed. No other mitigations are indicated. Patch status is confirmed by the vendor's fixed versions.