MikroTik · RouterOS
CVE-2026-67279
SSH Pre-Authentication Rekey State Bypass in MikroTik RouterOS
What it is
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)
CISA: Mikrotik RouterOS contains an improper enforcement of behavioral workflow vulnerability that could allow an unauthenticated client to open a session channel and send an exec request. This vulnerability can be chained to achieve unauthenticated exploitation of CVE-2026-86060.
What to do
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.
Deadline for US federal agencies: September 28, 2026
- Added to the CISA list
- September 25, 2026
- Published
- September 5, 2026
- Severity
- Medium 6.9 CVSS 4.0
- Chance of attacks in the next 30 days (EPSS)
- 2.3% in the top 17.0% of all known vulnerabilities
- Weakness
- CWE-841
- More details
- NVD · CVE.org · CISA
All references (7)
- https://mikrotik.com/supportsec/september-2026-vulnerability/
- https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve
- https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/
- https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/
- https://forum.mikrotik.com/t/6-49-21-long-term-is-released/272802
- https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801
- https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800
More exploited flaws from MikroTik
| Added | Vulnerability | Product | Severity | Attack chance |
|---|---|---|---|---|
| Sep 10, 2026 | Missing Authentication for Critical Function | RouterOS | High 8.8 | 1.6% |
| Sep 10, 2026 | Improper Neutralization of Argument Delimiters in a Command | RouterOS | Critical 9.2 | 6.4% |
| Sep 8, 2022 | Stack-Based Buffer Overflow | RouterOS | Critical 9.8 | 66% |
| Dec 1, 2021 | Router OS Directory Traversal | RouterOS | Critical 9.1 | 96% |
Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.