CVE-2026-67277

High

MikroTik RouterOS Missing Authentication for Critical Function Vulnerability

8.2 CVSS v3.1 CVSS v4.0: 8.8

Published: Sep 5, 2026
Updated: Sep 11, 2026
Vendor: Mikrotik
Affected versions: See affected products
Weakness: CWE-306

Summary

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

High (8.2)

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H

CVSS v4.0 (8.8)

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

Affected products

Mikrotik Routeros >= 6.0, < 6.49.21
Mikrotik Routeros >= 7.0, < 7.23.4
Mikrotik Routeros >= 7.24, < 7.24.2

Exploitation status

Actively exploited

Listed in the CISA Known Exploited Vulnerabilities catalog on Sep 10, 2026. Federal remediation due: Sep 13, 2026.

Technical details

Technical analysis has not been written for this record yet.

Mitigation & remediation

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.