MikroTik · RouterOS
CVE-2026-67277
Kernel memory disclosure and denial of service in MikroTik RouterOS btest service
What it is
RouterOS accepts a "related" btest connection before the corresponding primary session has completed authentication. An unauthenticated client can use this state to start an IPv4 UDP test. With "random-data=false", the sender transmits an uninitialized tail from a kernel packet buffer. A separate unchecked, inverted packet-size interval causes unsigned integer underflow, anomalously large fragmented output, and can restart the RouterOS kernel.
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 a missing authentication for critical function vulnerability which allows kernel memory disclosure and denial of service in the btest service.
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 13, 2026
- Added to the CISA list
- September 10, 2026
- Published
- September 5, 2026
- Severity
- High 8.8 CVSS 4.0
- Chance of attacks in the next 30 days (EPSS)
- 1.6% in the top 24.9% of all known vulnerabilities
- Weakness
- CWE-306
- 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 25, 2026 | Improper Enforcement of Behavioral Workflow | RouterOS | Medium 6.9 | 2.3% |
| 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.