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Actively exploited

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

MikroTik RouterOS contains a missing authentication for critical function vulnerability which allows kernel memory disclosure and denial of service in the btest service.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch urgentlyCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 10 Sep 2026.
  • Rated High severity (CVSS 8.8, scored by Vendor).
  • It has been in the catalogue for 57 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

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)

Affected Versions

ProductVersions
Mikrotik RouterOS7.24 to before 7.24.2
7.0.0 to before 7.23.4
6.0.0 to before 6.49.21

From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for MikroTik RouterOS. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    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.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated high, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 13 Sep 2026 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

More Exploited MikroTik Flaws

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CVE-2026-67279Mikrotik RouterOS Improper Enforcement of Behavioral Workflow VulnerabilityAdded 25 Sep 2026CVE-2026-86060MikroTik RouterOS Improper Neutralization of Argument Delimiters in a Command VulnerabilityAdded 10 Sep 2026CVE-2018-7445MikroTik RouterOS Stack-Based Buffer Overflow VulnerabilityAdded 8 Sep 2022CVE-2018-14847MikroTik Router OS Directory Traversal VulnerabilityAdded 1 Dec 2021

All 5 exploited MikroTik vulnerabilities

Not Sure If You Are Exposed?

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2026-67277
  3. CVE record: CVE-2026-67277
  4. FIRST EPSS
  5. mikrotik.com/supportsec/september-2026-vulnerability/
  6. cert.pl/en/posts/2026/09/mikrotik-routeros-cve
  7. cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/
  8. npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/
  9. forum.mikrotik.com/t/6-49-21-long-term-is-released/272802
  10. forum.mikrotik.com/t/7-23-4-long-term-is-released/272801
  11. forum.mikrotik.com/t/7-24-2-stable-is-released/272800