MikroTrick: Chained MikroTik RouterOS SSH Flaws Enable Unauthenticated Full Admin Takeover of Internet-Exposed Routers

MikroTik RouterOS 7.x fails to compare the complete RSA public key when matching an SSH authentication attempt against an authorized user key, checking the key type and modulus but omitting the exponent. Because RouterOS verifies the signature against the client-supplied key, an attacker who knows the modulus of an authorized RSA key can present a key with exponent 1 and a forged signature and be accepted as that user without possessing the private key. Successful exploitation opens an SSH command channel as the target user, giving the attacker control of the router without a password or key. Only the RouterOS 7.x branch is affected, with fixes released in 7.23.4 (Long-term) and 7.24.2 (Stable). A public proof-of-concept is available and related reporting describes active campaigns hijacking MikroTik routers using chained RouterOS flaws, though this CVE is not in CISA KEV and its 30-day EPSS probability is low (0.2%).

Do: Upgrade affected devices to RouterOS 7.23.4 (Long-term) or 7.24.2 (Stable) or later. Until patched, restrict SSH access to trusted management networks and, if feasible, remove or replace RSA authorized keys with other key types. Check devices for signs of compromise highlighted in recent reporting, such as an unexpected SSH user named '-2'.

CVE-2026-67279 is an authentication-ordering flaw (CWE-841) in the SSH server of MikroTik RouterOS: after a client-requested SSH rekey, the server enters the connection protocol even though user authentication was never attempted. An unauthenticated SSH client can therefore open a session channel and send an exec request, and on affected builds the server dispatches the command without any credentials. This lets the attacker create, overwrite, and reconstruct files in the RouterOS managed file namespace, including support files that contain configuration and diagnostic data. Any MikroTik device running RouterOS builds older than the fixed releases is affected, although remote exploitation requires the SSH service to be reachable by the attacker. No public proof-of-concept is known, the issue is not in CISA's KEV catalog, and EPSS estimates a 0.4% probability of exploitation in the next 30 days, so no exploitation is currently known.

Do: Upgrade RouterOS to 6.49.21 (Long-term v6), 7.23.4 (Long-term v7), or 7.24.2 (Stable). Until patched, restrict SSH access to trusted management networks/VPN or disable the SSH service where it is not needed. Review the RouterOS file list and SSH logs for unexpected or reconstructed files and session activity, since attackers have recently chained multiple MikroTik flaws against routers.

CVE-2026-86060 is an argument-injection flaw (CWE-88) in MikroTik RouterOS's SSH login path: when a login supplies a username beginning with a prohibited character, the RouterOS login helper mishandles the argument, allowing the trusted RouterOS policy mask to be changed and privileges to be escalated. An unauthenticated attacker only needs the ability to reach the router's SSH service, since exploitation happens during the SSH login process itself. By altering the policy mask the attacker gains elevated rights on the device, and news reports indicate attackers have used this technique — including logins with usernames such as '-2' — as part of chains that take over routers without needing a password. Any RouterOS deployment running versions before the fixes (6.49.21 Long-term, 7.23.4 Long-term, 7.24.2 Stable) with SSH enabled or reachable is affected, with internet-exposed SSH at highest risk. Multiple outlets report the RouterOS flaws are being actively exploited in the wild, although no public proof-of-concept is known and the flaw is not yet in CISA KEV.

Do: Upgrade RouterOS to 6.49.21 (Long-term), 7.23.4 (Long-term) or 7.24.2 (Stable) as applicable. Until patched, restrict SSH (TCP 22) to trusted management networks or disable the SSH service if unused, and review authentication logs and user/group policy settings for tampering — reports indicate attackers log in with usernames beginning with '-' (e.g., '-2').