Actively exploited · Published Sep 5, 2026 · Assigned by CERT-PL
CVE-2026-86060SSH session privilege manipulation via a crafted username in Mikrotik RouterOS
Critical 9.2 Exploited
In plain English
A critical-severity argument injection in RouterOS from Mikrotik. Attackers are actively exploiting it in the wild (listed by CISA on September 10, 2026). The chance it is exploited in the next 30 days is estimated at 6.4% (higher than 94% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. 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.
CISA guidance
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.
Federal agencies must remediate by Sep 13, 2026.
Official description
RouterOS contains an argument-handling flaw in the SSH login path involving usernames that begin with a prohibited character, allowing for the trusted RouterOS policy mask to be changed, leading to privilege escalation. Exploitation requires an unauthenticated SSH session to reach the RouterOS login helper.This issue was fixed in versions: 6.49.21 (Long-term), 7.23.4 (Long-term) and 7.24.2 (Stable)
Affected products (as reported)
Weakness: CWE-88 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
References
- https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve third-party-advisory
- https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/ technical-description
- https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/ exploit
- https://mikrotik.com/supportsec/september-2026-vulnerability/ vendor-advisory
- https://forum.mikrotik.com/t/6-49-21-long-term-is-released/272802 release-notes
- https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801 release-notes
- https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800 release-notes
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-86060 government-resource