- High 8.8
- Known exploited (CISA KEV)
CVE-2026-67277
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)
Scores
The facts
- Published
- 5 September 2026
- Last changed
- 11 September 2026
- NVD status
- Analyzed
- Severity
- High, CVSS 8.8 out of 10 (version 4.0)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R… - Weakness
- Affects
- mikrotik routeros
- Known exploited
- Yes. CISA added it to the Known Exploited Vulnerabilities catalogue on 10 September 2026.
- EPSS
- 1.6% chance of exploitation activity in the next 30 days (percentile 75).
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