Vulnerability Report

CVE-2026-67277

CISA KEV Active

Title: CVE-2026-67277

Auth Bypass

Proof Of Concept

No public PoC currently indexed for CVE-2026-67277.

CWE Category CWE-306

Published Date Sep 05, 2026

Modified Date Sep 11, 2026

Exploit Status Not Found

Score 8.8 CVSS v4.0

Exploit Probability (EPSS)

0.44%

Vulnerability Summary

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)

Impacted Vendors

Analysis in Progress...

Reference Links

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 https://mikrotik.com/supportsec/september-2026-vulnerability/ https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/

CVSS v4.0

Source Entity [email protected]

Severity HIGH

8.8

Attack Vector

NETWORK

Complexity

LOW

Privileges

N/A

Interaction

NONE

Confidentiality

N/A

Integrity

N/A

Availability

N/A

Scope

N/A

RAW VECTOR

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:X/V:X/RE:X/U:X

Associated Attack Patterns (CAPEC)

Total: Patterns