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)
Metrics
CVSS 3.1 8.2/10
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:HWeakness enumeration
Affected software
| Vendor | Product | Versions |
|---|---|---|
| Mikrotik | RouterOS | >= 7.24, < 7.24.2; >= 7.0.0, < 7.23.4; >= 6.0.0, < 6.49.21 |
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-exploited/Mitigation, Third 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-they-wouldnt-explain/Exploit, Third Party Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-67277US Government Resource
Timeline
- Published
- Sep 5, 2026
- Last modified
- Sep 11, 2026
- Added to CISA KEV
- Sep 10, 2026
- NVD status
- Analyzed