MikroTik RouterOS TLS Forgery: RSA PKCS#1 v1.5 Signature (e=3) Pre-6.49.21
CVE-2026-67278 Published on September 5, 2026
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 roots 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.
Vulnerability Analysis
CVE-2026-67278 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. Public availability of a proof of concept (POC) exploit exists for CVE-2026-67278. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity and availability.
Weakness Type
Improper Verification of Cryptographic Signature
The software does not verify, or incorrectly verifies, the cryptographic signature for data.
Products Associated with CVE-2026-67278
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Affected Versions
Mikrotik RouterOS:- Version 7.24 and below 7.24.3 is affected.
- Version 7.0.0 and below 7.23.6 is affected.