Vulnerability Description
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)
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Mikrotik | Routeros | >= 6.0, < 6.49.21 |
Related Weaknesses (CWE)
References
- https://cert.pl/en/posts/2026/09/mikrotik-routeros-cveThird Party Advisory
- https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-eMitigationThird Party Advisory
- https://forum.mikrotik.com/t/6-49-21-long-term-is-released/272802Release Notes
- https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801Release Notes
- https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800Release Notes
- https://mikrotik.com/supportsec/september-2026-vulnerability/Vendor Advisory
- https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-thExploitThird Party Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-US Government Resource
FAQ
What is CVE-2026-67277?
CVE-2026-67277 is a vulnerability with a CVSS score of 8.2 (HIGH). 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 "rando...
How severe is CVE-2026-67277?
CVE-2026-67277 has been rated HIGH with a CVSS base score of 8.2/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-67277?
Check the references section above for vendor advisories and patch information. Affected products include: Mikrotik Routeros.