CVSS 4.0
8.8 highCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:NCVE-2026-67277
High (8.8) in MikroTik RouterOS. In CISA KEV since 2026-09-10. EPSS 1.6% chance of exploitation in the next 30 days.
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)
Severity
CVSS 3.1
8.2 highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H- EPSS
- 1.6% chance of exploitation in the next 30 days; higher than 75% of CVEs (scores of 2026-10-31)
- CISA KEV
- listed 2026-09-10, due 2026-09-13
- CWE
- CWE-306
- Published
- Modified
- Record from
- the NVD, synced
Affected
- mikrotik:routeros
References
- https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve
- https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/
- 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