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Known Exploited Vulnerability
8.8
HIGH CVSS 4.0
CVE-2026-67277
MikroTik RouterOS Missing Authentication for Critical Function Vulnerability - [Actively Exploited]
Overview
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)

Details
INFO

Published Date :

Sept. 5, 2026, 8:17 p.m.

Last Modified :

Sept. 11, 2026, 12:52 p.m.

Remotely Exploit :

Yes !

Source :

[email protected]
CISA Notification
CISA KEV (Known Exploited Vulnerabilities)

For the benefit of the cybersecurity community and network defenders—and to help every organization better manage vulnerabilities and keep pace with threat activity—CISA maintains the authoritative source of vulnerabilities that have been exploited in the wild.

Description :

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

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.

Known Ransomware Campaign Use:

Unknown

Notes :

https://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

Impact
Affected Products

The following products are affected by CVE-2026-67277 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Mikrotik routeros
2 Mikrotik routeros
: Total Affected Vendor : 1 | Products : 2
Scoring
CVSS Scores
The Common Vulnerability Scoring System is a standardized framework for assessing the severity of vulnerabilities in software and systems. We collect and displays CVSS scores from various sources for each CVE.
Score Version Severity Vector Exploitability Score Impact Score Source
CVSS 134c704f-9b21-4f2e-91b3-4a467353bcc0
CVSS 3.1 HIGH [email protected]
CVSS 4.0 HIGH 4bb8329e-dd38-46c1-aafb-9bf32bcb93c6
CVSS 4.0 HIGH [email protected]
Solution
Update RouterOS to a fixed version to prevent kernel restarts and anomalous output.
  • Update RouterOS to 6.49.21 or later.
  • Update RouterOS to 7.23.4 or later.
  • Update RouterOS to 7.24.2 or later.
References
References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2026-67277.

URL Resource
https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve Third Party Advisory
https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/ Mitigation Third Party Advisory
https://forum.mikrotik.com/t/6-49-21-long-term-is-released/272802 Release Notes
https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801 Release Notes
https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800 Release Notes
https://mikrotik.com/supportsec/september-2026-vulnerability/ Vendor Advisory
https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/ Exploit Third Party Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-67277 US Government Resource
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-67277 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-67277 weaknesses.

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2026-67277 vulnerability anywhere in the article.

  • cert.pl
MikroTrick: technical analysis, disclosure process, and the use of LLM agents

Introduction On 3 September 2026, MikroTik released patches almost simultaneously for several maintained RouterOS branches: 7.25beta3, 7.24.2, 7.23.4, and 6.49.21, and recommended installing a patched ... Read more

Published Date: Sep 22, 2026 (3 days, 14 hours ago)
  • security.nl
2,6 miljoen MikroTik-routers draaien met publiek toegankelijke services

maandag 14 september 2026, 10:39 door Redactie, 0 reactiesLaatst bijgewerkt: Vandaag, 11:00 Wereldwijd zijn er zo'n 2,6 miljoen MikroTik-routers, waarvan ruim achtduizend in Nederland, die met publiek ... Read more

Published Date: Sep 14, 2026 (1 week, 4 days ago)
  • The Hacker News
CISA Adds 5 Actively Exploited Artifactory, ScreenConnect, and RouterOS Flaws to KEV

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added five security flaws impacting JFrog Artifactory, ConnectWise ScreenConnect, and MikroTik RouterOS to its Known Exploited Vuln ... Read more

Published Date: Sep 12, 2026 (1 week, 6 days ago)
  • TheCyberThrone
CISA adds Six Vulnerabilities in Two Days

CISA added six vulnerabilities to the Known Exploited Vulnerabilities (KEV) Catalog across September 10 and 11, 2026.The additions affect MikroTik RouterOS, ConnectWise ScreenConnect, GitLab, and JFro ... Read more

Published Date: Sep 12, 2026 (1 week, 6 days ago)
  • The Cyber Express
Attackers Exploited MikroTik RouterOS Flaws a Day Before Patches Shipped

Attackers began compromising internet-exposed MikroTik routers on Sept. 2, a day before the Latvian vendor released fixes and three days before national authorities published the technical detail defe ... Read more

Published Date: Sep 07, 2026 (2 weeks, 4 days ago)
  • cert.pl
Vulnerabilities in Mikrotik RouterOS software

Vulnerabilities in Mikrotik RouterOS software CVE ID CVE-2026-67276 Publication date 05 September 2026 Vendor Mikrotik Product RouterOS Vulnerable versions From 7.24 below 7.24.2From 7.0.0 below 7.23. ... Read more

Published Date: Sep 05, 2026 (2 weeks, 6 days ago)
  • cert.pl
Critical vulnerabilities in MikroTik RouterOS are being actively exploited. Immediate update recommended

The CERT Polska team has identified and coordinated the disclosure of six vulnerabilities in MikroTik RouterOS. Combining two of them allows an attacker to take full control of the device without auth ... Read more

Published Date: Sep 05, 2026 (2 weeks, 6 days ago)

Results are limited to the first 20 news articles due to potential performance issues.

The following table lists the changes that have been made to the CVE-2026-67277 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • Initial Analysis by [email protected]

    Sep. 11, 2026

    Action Type Old Value New Value
    Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
    Added CPE Configuration OR *cpe:2.3:o:mikrotik:routeros:*:*:*:*:*:*:*:* versions from (including) 6.0 up to (excluding) 6.49.21 *cpe:2.3:o:mikrotik:routeros:*:*:*:*:*:*:*:* versions from (including) 7.0 up to (excluding) 7.23.4 *cpe:2.3:o:mikrotik:routeros:*:*:*:*:*:*:*:* versions from (including) 7.24 up to (excluding) 7.24.2
    Added Reference Type CERT.PL: https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve Types: Third Party Advisory
    Added Reference Type CERT.PL: https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/ Types: Mitigation, Third Party Advisory
    Added Reference Type CERT.PL: https://forum.mikrotik.com/t/6-49-21-long-term-is-released/272802 Types: Release Notes
    Added Reference Type CERT.PL: https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801 Types: Release Notes
    Added Reference Type CERT.PL: https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800 Types: Release Notes
    Added Reference Type CERT.PL: https://mikrotik.com/supportsec/september-2026-vulnerability/ Types: Vendor Advisory
    Added Reference Type CERT.PL: https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/ Types: Exploit, Third Party Advisory
    Added Reference Type CISA-ADP: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-67277 Types: US Government Resource
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Sep. 11, 2026

    Action Type Old Value New Value
    Changed SSVC {'id': 'CVE-2026-67277', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'active'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-09-10T19:48:06.780837Z'} {'id': 'CVE-2026-67277', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'active'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-09-08T00:00:00+00:00'}
  • CVE CISA KEV Update by 9119a7d8-5eab-497f-8521-727c672e3725

    Sep. 10, 2026

    Action Type Old Value New Value
    Added Date Added 2026-09-10
    Added Due Date 2026-09-10
    Added Required Action 2026-09-10
    Added Vulnerability Name 2026-09-10
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Sep. 10, 2026

    Action Type Old Value New Value
    Added Reference https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-67277
    Changed SSVC {'id': 'CVE-2026-67277', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-09-08T00:00:00+00:00'} {'id': 'CVE-2026-67277', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'active'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-09-10T19:48:06.780837Z'}
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Sep. 09, 2026

    Action Type Old Value New Value
    Changed SSVC {'id': 'CVE-2026-67277', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-09-08T15:21:10.527320Z'} {'id': 'CVE-2026-67277', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-09-08T00:00:00+00:00'}
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Sep. 08, 2026

    Action Type Old Value New Value
    Added SSVC {'id': 'CVE-2026-67277', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-09-08T15:21:10.527320Z'}
  • CVE Modified by [email protected]

    Sep. 05, 2026

    Action Type Old Value New Value
    Changed 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 (Lont-term), 7.23.4 (Lont-term) and 7.24.2 (Stable) 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)
  • New CVE Received by [email protected]

    Sep. 05, 2026

    Action Type Old Value New Value
    Added 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 (Lont-term), 7.23.4 (Lont-term) and 7.24.2 (Stable)
    Added CVSS V4.0 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
    Added CWE CWE-306
    Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/67xxx/CVE-2026-67277.json">CVE-2026-67277</a>
    Added Reference https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve
    Added Reference https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/
    Added Reference https://forum.mikrotik.com/t/6-49-21-long-term-is-released/272802
    Added Reference https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801
    Added Reference https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800
    Added Reference https://mikrotik.com/supportsec/september-2026-vulnerability/
    Added Reference https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
CVSS
Vulnerability Scoring Details
Base CVSS Score: 8.8
Attack Vector
Attack Complexity
Attack Requirements
Privileges Required
User Interaction
VS Confidentiality
VS Integrity
VS Availability
SS Confidentiality
SS Integrity
SS Availability
Base CVSS Score: 8.2
Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality Impact
Integrity Impact
Availability Impact