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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-67277
StatePUBLISHED
AssignerCERT-PL
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-05 20:17:18 UTC
Updated2026-09-11 12:52:29 UTC
DescriptionRouterOS 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)

Risk And Classification

Primary CVSS: v4.0 8.8 HIGH from [email protected]

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

EPSS: 0.015600000 probability, percentile 0.742560000 (date 2026-09-29)

CISA KEV: Listed on 2026-09-10; due 2026-09-13; ransomware use Unknown

Problem Types: CWE-306 | CWE-306 CWE-306 Missing authentication for critical function

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary8.8HIGHCVSS: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/C...
4.0CNACVSS8.8HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N
3.1[email protected]Primary8.2HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Confidentiality
Low
Integrity
None
Availability
High
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

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

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H

CISA Known Exploited Vulnerability

VendorMikroTik
ProductRouterOS
NameMikroTik RouterOS Missing Authentication for Critical Function Vulnerability
Required ActionApply 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.
Noteshttps://mikrotik.com/supportsec/september-2026-vulnerability/ ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: 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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Mikrotik Routeros All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mikrotik RouterOS affected 7.24 7.24.2 custom Not specified
CNA Mikrotik RouterOS affected 7.0.0 7.23.4 custom Not specified
CNA Mikrotik RouterOS affected 6.0.0 6.49.21 custom Not specified

References

ReferenceSourceLinkTags
cert.pl/en/posts/2026/09/mikrotik-routeros-cve [email protected] cert.pl Third Party Advisory
npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they... [email protected] npratley.net Exploit, Third Party Advisory
www.cisa.gov/known-exploited-vulnerabilities-catalog 134c704f-9b21-4f2e-91b3-4a467353bcc0 www.cisa.gov US Government Resource
forum.mikrotik.com/t/6-49-21-long-term-is-released/272802 [email protected] forum.mikrotik.com Release Notes
cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-activel... [email protected] cert.pl Mitigation, Third Party Advisory
forum.mikrotik.com/t/7-23-4-long-term-is-released/272801 [email protected] forum.mikrotik.com Release Notes
forum.mikrotik.com/t/7-24-2-stable-is-released/272800 [email protected] forum.mikrotik.com Release Notes
mikrotik.com/supportsec/september-2026-vulnerability [email protected] mikrotik.com Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
CISA Known Exploited Vulnerabilities catalog CISA www.cisa.gov kev

Vendor Comments And Credit

Discovery Credit

CNA: Sławomir Rozbicki (CERT.PL) (en)

Additional Advisory Data

SourceTimeEvent
ADP2026-09-10T00:00:00.000ZCVE-2026-67277 added to CISA KEV

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