MikroTik RouterOS SSH flaws exploited in wild
Attackers are chaining three MikroTik RouterOS vulnerabilities to gain full control of routers with internet-exposed SSH; patches available.
Sourceadvisories.ncsc.nl — open the original
What to check
- Applies to
- The 3 CVEs named below. Whether you run an affected version is not assessed: check the versions the source lists.
- Exploitation
- CISA lists CVE-2026-67277 and CVE-2026-86060 as exploited in the wild.
NCSC-NL published an advisory detailing three vulnerabilities in MikroTik RouterOS that CERT Polen has observed being actively exploited in combination against routers with SSH services exposed to the internet. The first flaw (CVE-2026-67276) stems from improper verification of RSA signature exponents in the SSH authentication mechanism, allowing attackers to forge RSA signatures and obtain unauthorized SSH access. The second (CVE-2026-86060) involves usernames beginning with a disallowed character that can manipulate the trusted policy mask, enabling privilege escalation during the SSH login process. The third (CVE-2026-67277) allows unauthenticated clients to trigger an IPv4 UDP test that, due to improper kernel packet handling, can cause kernel restarts and denial of service.
According to the advisory, in observed attacks multiple of these vulnerabilities were chained together to gain full control over affected routers. MikroTik has released fixed versions — RouterOS 6.49.21, 7.23.4 and 7.24.2 — addressing all three issues. NCSC-NL and MikroTik recommend not exposing SSH directly to the internet, instead restricting access via VPN and/or IP whitelisting as a mitigating control while patching is completed.
Defenders operating MikroTik RouterOS devices should prioritize patching to the fixed versions, audit for internet-facing SSH exposure, and review authentication logs for anomalous SSH logins or unexpected kernel restarts that could indicate exploitation attempts.
Mentioned in this report
Source reporting: https://advisories.ncsc.nl/2026/ncsc-2026-0345.html
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