CVE-2026-67277
KEV: known exploited SSVC: activeKernel memory disclosure and denial of service in MikroTik RouterOS btest service
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
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
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
Attack conditions and impact
Derived from the NVD CVSS 3.1 vectorThis vulnerability may be exploitable over the internet without authentication or user interaction.
| Metric | Value | Meaning |
|---|---|---|
| Attack vector AV | N | Network |
| Attack complexity AC | L | Low (easy) |
| Privileges required PR | N | None |
| User interaction UI | N | None |
| Scope S | U | Unchanged |
| Confidentiality C | L | Low |
| Integrity I | N | None |
| Availability A | H | High |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
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)
CISA KEV entry
MikroTik RouterOS Missing Authentication for Critical Function Vulnerability — MikroTik / RouterOS
MikroTik RouterOS contains a missing authentication for critical function vulnerability which allows kernel memory disclosure and denial of service in the btest service.
Required action: 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.
https://mikrotik.com/supportsec/september-2026-vulnerability/ ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2026-67277
CVSS assessments
| Provider | Version | Score | Vector |
|---|---|---|---|
| NVD / [email protected] (Secondary) | 4.0 | 8.8 HIGH | 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 |
| NVD / [email protected] (Primary) | 3.1 | 8.2 HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H |
| CNA / CERT-PL | 4.0 | 8.8 HIGH | 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 |
Affected products and packages
CNA (CVE.org)
| Vendor | Product | Versions |
|---|---|---|
| Mikrotik | RouterOS | affected: 7.24 … < 7.24.2 affected: 7.0.0 … < 7.23.4 affected: 6.0.0 … < 6.49.21 default: unaffected |
NVD CPE (3)
Show CPE list
| Vendor | Product | Range | CPE |
|---|---|---|---|
| mikrotik | routeros | >= 6.0, < 6.49.21 | cpe:2.3:o:mikrotik:routeros:*:*:*:*:*:*:*:* |
| mikrotik | routeros | >= 7.0, < 7.23.4 | cpe:2.3:o:mikrotik:routeros:*:*:*:*:*:*:*:* |
| mikrotik | routeros | >= 7.24, < 7.24.2 | cpe:2.3:o:mikrotik:routeros:*:*:*:*:*:*:*:* |
Linux distribution status
References (8)
- https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve NVD, CNA Third Party Advisorythird-party-advisory
- https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/ NVD, CNA MitigationThird Party Advisorytechnical-description
- https://forum.mikrotik.com/t/6-49-21-long-term-is-released/272802 NVD, CNA Release Notesrelease-notes
- https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801 NVD, CNA Release Notesrelease-notes
- https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800 NVD, CNA Release Notesrelease-notes
- https://mikrotik.com/supportsec/september-2026-vulnerability/ NVD, CNA Vendor Advisoryvendor-advisory
- https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/ NVD, CNA ExploitThird Party Advisoryexploit
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-67277 NVD, ADP CISA-ADP US Government Resourcegovernment-resource