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CVE-2026-67277: MikroTik RouterOS Missing Authentication (CVSS 8.8)

CVE-2026-67277 is a high severity missing authentication in MikroTik RouterOS with a CVSS score of 8.8. It is listed in the CISA Known Exploited Vulnerabilities catalog, so treat it as an active threat and patch immediately.

Last updated: Sep 11, 2026

Quick answer

Direct answer

CVE-2026-67277 is a high severity missing authentication in MikroTik RouterOS with a CVSS score of 8.8. It is listed in the CISA Known Exploited Vulnerabilities catalog, so treat it as an active threat and patch immediately.

Risk scores

CVSS base score
8.8HIGH
EPSS probability
1.56%
Higher than 75 percent of all CVEs
CISA KEV
Exploited Yes
Added Sep 10, 2026
CVSS metricWhat it means
Attack vector (AV:N)Network: reachable remotely
Attack complexity (AC:L)Low complexity
Attack requirements (AT:N)No attack requirements
Privileges required (PR:N)No privileges required
User interaction (UI:N)No user interaction
Confidentiality (VC:L)Low confidentiality impact
Integrity (VI:N)No integrity impact
Availability (VA:H)High availability impact

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

CISA 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.

About MikroTik RouterOS

CVE-2026-67277 affects MikroTik RouterOS, a product from MikroTik. Before acting, confirm where MikroTik RouterOS runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.

What the flaw is

In plain terms: 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)

The weakness class is Missing Authentication. A critical function can be used without logging in.

Based on its CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. It is listed in the CISA Known Exploited Vulnerabilities catalog, so treat it as an active threat and patch immediately.

Affected versions and timeline

FieldDetail
ProductMikroTik RouterOS
Affected versionsRouteros from 6.0 before 6.49.21; Routeros from 7.0 before 7.23.4; Routeros from 7.24 before 7.24.2
PublishedSep 5, 2026
Last modifiedSep 11, 2026
Added to CISA KEVSep 10, 2026
Assigning CNAcvd@cert.pl

How to detect it

  • Inventory every instance of MikroTik RouterOS and record the running version against the affected range above.
  • Check external attack surface scans for internet facing instances of the component.
  • Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
  • Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.

How to fix it

  • Apply the fixed version of MikroTik RouterOS named in the vendor advisory.
  • If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
  • Rescan after the change to prove the exposure is gone, then close the ticket.

CTEM action plan

CTEM stageWhat to do for this CVE
ScopeAdd every business service that depends on MikroTik RouterOS to the current CTEM cycle.
DiscoverFind all instances, including shadow and cloud deployments, and record versions and exposure.
PrioritizeKnown exploited, so top priority.
ValidateConfirm the flaw is reachable and exploitable in your environment and that compensating controls work.
MobilizeAssign the fix to the asset owner with a due date matched to the priority, then verify closure.

CWE References

Technical References

Frequently asked questions

CVE-2026-67277 is a high severity missing authentication in MikroTik RouterOS with a CVSS score of 8.8. It is listed in the CISA Known Exploited Vulnerabilities catalog, so treat it as an active threat and patch immediately.

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