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CVE-2026-67277

8.2 · HIGHActively Exploited

RouterOS accepts a "related" btest connection before the corresponding primary session has completed authentication.

Published Sep 5, 2026mikrotikCWE-306EPSS 1.56%

Overview

CVE-2026-67277 is a high-severity vulnerability affecting mikrotik routeros. It was published on September 5, 2026 and has a CVSS 3.1 base score of 8.2 (HIGH). This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog, indicating active exploitation in the wild.

This vulnerability has a CVSS 3.1 base score of 8.2, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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)

Remediation

Check the references section for vendor advisories and patches from mikrotik. Update routeros to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected products

VendorProductVersionsStatus
mikrotikrouteros>= 6.0, < 6.49.21Affected

References

Refcert.pl/en/posts/2026/09/mikrotik-routeros-cveRefcert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/Refforum.mikrotik.com/t/6-49-21-long-term-is-released/272802Refforum.mikrotik.com/t/7-23-4-long-term-is-released/272801Refforum.mikrotik.com/t/7-24-2-stable-is-released/272800Refmikrotik.com/supportsec/september-2026-vulnerability/Refnpratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/CISAwww.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-67277

How CyberStrike helps

Frequently asked questions

What is CVE-2026-67277?

CVE-2026-67277 is a high-severity vulnerability affecting mikrotik routeros. It was published on September 5, 2026 and has a CVSS 3.1 base score of 8.2 (HIGH). This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog, indicating active exploitation in the wild.

How severe is CVE-2026-67277?

This vulnerability has a CVSS 3.1 base score of 8.2, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-67277?

Check the references section for vendor advisories and patches from mikrotik. Update routeros to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-67277?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-67277 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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