CVE-2026-67277: MikroTik RouterOS Missing Authentication for Critical Function Vulnerability

CISA Known Exploited Vulnerabilities

Name

MikroTik RouterOS Missing Authentication for Critical Function Vulnerability

Vendor

MikroTik

Product

RouterOS

Added to the catalog

2026-09-10

Due date for US federal agencies

2026-09-13

Weaknesses

CWE-306

Catalog version

2026.10.30

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 (CISA)

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.

Ransomware use: CISA does not mark known use of this vulnerability in ransomware campaigns.

Links in CISA's notes

• https://mikrotik.com/supportsec/september-2026-vulnerability/
• https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk
• 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

Read on 2026-11-02T23:39:54.475Z under licence cisa-kev-cc0@b0067899 from https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

NVD analysis

Status

Analyzed

Published

2026-09-05T20:17:18.120

Last modified

2026-09-11T12:52:29.533

Weaknesses

CWE-306

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)

References

• https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve (Third 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/272802 (Release Notes)
• https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801 (Release Notes)
• https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800 (Release 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-2026-67277 (US Government Resource)

This product uses the NVD API but is not endorsed or certified by the NVD.

Read on 2026-11-02T23:42:31.494Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-67277

CVE record

Title (CNA)

Kernel memory disclosure and denial of service in MikroTik RouterOS btest service

Assigner

CERT-PL

State

PUBLISHED

Published

2026-09-05T20:00:56.614Z

Updated

2026-09-11T03:55:58.675Z

Problem types

CWE-306 Missing authentication for critical function

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)

References

• https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve
• https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/
• https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/
• https://mikrotik.com/supportsec/september-2026-vulnerability/
• 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

Read on 2026-11-03T02:20:54.435Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/67xxx/CVE-2026-67277.json

Defensive techniques (MITRE D3FEND)

D3FEND maps these defensive techniques to the weakness (CWE) that NVD lists for this CVE, through the digital artifacts the weakness affects. D3FEND does not say they stop this vulnerability.

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