MikroTik RouterOS's Missing Authentication for a Critical Function Allows Unauthenticated Attackers to Access and Modify Router Configuration; CISA's September 13th KEV Deadline Has Passed

Last refreshed2026-09-27

Status: KEV | Advisory ID: CVE-2026-67277

Key Details

CVE	CVE-2026-67277
Vulnerability Name	MikroTik RouterOS Missing Authentication for Critical Function Vulnerability
CVSS Score / Version	8.2 (High) / CVSS v3.1
Updated	2026-09-20
CVSS Vector	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H`
CVSS Prose	attack vector is network; attack complexity is low; privileges required is none; user interaction is none; scope is unchanged; confidentiality impact is low; integrity impact is none; availability impact is high.
Affected products	MikroTik RouterOS
Exploitation status	Listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating confirmed active exploitation.
Classified as	CWE-306 (Missing Authentication for Critical Function)
KEV listing	Added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2026-09-10.
Exploitation prediction (EPSS)	1.56% probability of exploitation in the next 30 days (74% percentile) -- FIRST.org's EPSS model.
Federal remediation deadline	2026-09-13 (CISA KEV, Binding Operational Directive).

Affected Products, Subsystems & Sectors

Vendor	Product	Affected Versions	Patch Status
MikroTik	RouterOS

Vendor

Product

Affected Versions

Patch Status

MikroTik

RouterOS

Subsystems	Industrial Network - Routers/Firewalls
Sectors	Multi-sector

What to Know

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)

What to Do

Monitor MikroTik's web page for any future patch releases. See vendor advisory link below.

References

Source	Reference
NVD	https://nvd.nist.gov/vuln/detail/CVE-2026-67277
CVE	https://www.cve.org/CVERecord?id=CVE-2026-67277
Vendor advisory	https://mikrotik.com/supportsec/september-2026-vulnerability/

Source

Reference

NVD

https://nvd.nist.gov/vuln/detail/CVE-2026-67277

CVE

https://www.cve.org/CVERecord?id=CVE-2026-67277

Vendor advisory

https://mikrotik.com/supportsec/september-2026-vulnerability/

KEV Required Action

Field	Value
KEV Link	https://www.cisa.gov/known-exploited-vulnerabilities-catalog
Date Added to KEV	2026-09-10
Required Action Due Date	2026-09-13
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.

Field

Value

KEV Link

https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Date Added to KEV

2026-09-10

Required Action Due Date

2026-09-13

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.