How to fix CVE-2026-67279: MikroTik RouterOS (exploited in the wild)

RouterOS SSH enters the connection protocol after a client-requested rekey even though user authentication was never attempted, allowing an unauthenticated client to open a session channel and send an exec request. On affected builds the server dispatches the command, enabling unauthenticated creation, overwrite, and reconstruction of files in the RouterOS managed file namespace, including support files containing configuration and diagnostic data.This issue was fixed in versions: 6.49.21 (Long-term), 7.23.4 (Long-term) and 7.24.2 (Stable)

• Severity: MEDIUM (CVSS 4.0 6.9, vector CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N).
• Weakness: CWE-841.
• NVD published 2026-09-05, status Analyzed.

Anyone running MikroTik RouterOS in the version ranges below. Internet-facing instances are the priority.

• mikrotik routeros: from 6.0 up to (not including) 6.49.21.
• mikrotik routeros: from 7.0 up to (not including) 7.23.4.
• mikrotik routeros: from 7.24 up to (not including) 7.24.2.

Version ranges come from the NVD CPE configuration. Confirm against the vendor advisory before you rely on them.

• Exploited in the wild: added to the CISA Known Exploited Vulnerabilities catalog on 2026-09-25; federal remediation due date 2026-09-28.
• Public proof-of-concept code: 4 GitHub repositories from 4 accounts, the first on 2026-09-26.

• EPSS (probability of exploitation activity in the next 30 days): 1.05%, higher than 64% of all scored CVEs (as of 2026-10-24).
• CVERadar threat level: 50/100 (see methodology).
• Likely ATT&CK techniques: T1190 Exploit Public-Facing Application (inferred).

1. Find every instance. List where MikroTik RouterOS runs, including test, DR and forgotten internet-facing systems, and record the installed version.
2. Upgrade to a fixed release. mikrotik routeros: 6.49.21 or later; mikrotik routeros: 7.23.4 or later; mikrotik routeros: 7.24.2 or later. Get the build from the vendor advisory.
3. If you can't patch today, follow CISA's required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
4. Verify the fix. Re-run the version check on every instance and confirm it reports the fixed build (6.49.21 or later). Re-scan from outside if the service is exposed.
5. Hunt for signs of earlier compromise. If the system was exposed before you patched, assume it may have been hit and check the items below.
6. Rotate credentials stored on or used by the affected system if you cannot rule out compromise, and keep the logs you reviewed.

Detection hints

• T1190 Exploit Public-Facing Application: Review WAF, reverse-proxy and application logs for unusual requests to RouterOS (odd paths, oversized or encoded payloads, bursts of errors), going back to at least 2026-09-05.

Detection commands are generic starting points, not CVE-specific signatures. Use the indicators from the vendor advisory when it publishes them.

• NVD: CVE-2026-67279 nvd.nist.gov/vuln/detail/CVE-2026-67279
• CVE.org record www.cve.org/CVERecord?id=CVE-2026-67279
• Vendor link from CISA KEV mikrotik.com/supportsec/september-2026-vulnerability
• Mitigation cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively
• Release Notes forum.mikrotik.com/t/6-49-21-long-term-is-released/272802
• Release Notes forum.mikrotik.com/t/7-23-4-long-term-is-released/272801
• Release Notes forum.mikrotik.com/t/7-24-2-stable-is-released/272800
• Vendor Advisory mikrotik.com/supportsec/september-2026-vulnerability/
• CISA KEV catalog www.cisa.gov/known-exploited-vulnerabilities-catalog
• FIRST EPSS (2026-10-24) api.first.org/data/v1/epss?cve=CVE-2026-67279