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 breakdown
CVSS 4.0
Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Confidentiality (Vulnerable System)
Low
Integrity (Vulnerable System)
None
Availability (Vulnerable System)
High
Confidentiality (Subsequent System)
None
Integrity (Subsequent System)
None
Availability (Subsequent System)
None
CVSS 3.1
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
High
Affected products
- MikroTik / RouterOS7.24 – 7.24.2
- MikroTik / RouterOS7.0.0 – 7.23.4
- MikroTik / RouterOS6.0.0 – 6.49.21
- MikroTik / RouterOS6.0 – 6.49.21
References
- MISChttps://cert.pl/en/posts/2026/09/mikrotik-routeros-cve
- MISChttps://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/
- MISChttps://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/
- MISChttps://mikrotik.com/supportsec/september-2026-vulnerability/
- MISChttps://forum.mikrotik.com/t/6-49-21-long-term-is-released/272802
- MISChttps://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801
- MISChttps://forum.mikrotik.com/t/7-24-2-stable-is-released/272800
Updated 9m ago · 8 sources