CriticalCVE-2026-67277

Kernel memory disclosure and denial of service in MikroTik RouterOS btest service (CVE-2026-67277)

Published 05.09.2026Last modified 11.09.2026In CISA KEV since 10.09.2026Sources: pwn.watch, CVE.org, EUVD, BSI

What is affected, what to do

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.

The vulnerability is being actively exploited; treat it as a priority. Update Mikrotik RouterOS to version 7.24.2, Mikrotik RouterOS to version 7.23.4, Mikrotik RouterOS to version 6.49.21. Immediate actions, mitigation and detection rules are in the runbook below.

Affected: Mikrotik RouterOS lt 7.24..7.24.2
Mikrotik RouterOS lt 7.0.0..7.23.4
Mikrotik RouterOS lt 6.0.0..6.49.21
Fixed in: Mikrotik RouterOS 7.24.2
Mikrotik RouterOS 7.23.4
Mikrotik RouterOS 6.49.21

Not sure whether and how you are affected? Ask a question about this vulnerability

Metrics

8.8

Priority

XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

Source: Vendor (CNA), CVSS v4

8.2

CVSS v3

Severity High on the scale from 0 to 10.

Source: pwn.watch, CVE.org, EUVD, BSI

1.6 %

EPSS score

Moderate — model estimates 1-10% exploitation likelihood.

Source: FIRST EPSS, percentile 75.2

Show all metrics

Severity: Critical
Priority (0–325) The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first? Read in glossary: 214.67 Methodology
Exploit maturity An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack. Read in glossary: actively exploitedSource: VulnCheck KEV (opens in a new tab) How we classify
XIEM Effective CVSS XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command. Read in glossary: 8.8 Methodology
CVSS v3 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 8.2
CVSS v4 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 8.8
EPSS score The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“. Read in glossary: 1.6 %; Moderate — model estimates 1-10% exploitation likelihood.
EPSS percentile The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking. Read in glossary: 75.2; High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
KEV status The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: Actively exploited
Published: 05.09.2026
In CISA KEV since The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: 10.09.2026
CISA assessment (SSVC): Exploitation: active · automatable · Technical impact: partial; Source: CISA Vulnrichment, as of 8 September 2026
CWE CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect. Read in glossary: CWE-306

Response and mitigation

Why act now?

Prioritisation rationale

This CVE landed on CISA KEV because it is network-reachable without authentication and lets an attacker either leak kernel memory or crash the device at will — on edge routers and VPN concentrators that translates directly into loss of connectivity and potential disclosure of adjacent session fragments. MikroTik devices are extremely common at the perimeter of European WISP, hosting and industrial environments and are routinely weaponised for botnet recruitment and infrastructure pivoting, so active exploitation attempts should be assumed. Rate HIGH for every internet-exposed RouterOS instance and MEDIUM for internally segmented devices; the absence of a confirmed ransomware campaign only marginally lowers impact, since availability (A:H) is a core NIS2 risk category.

01
Runbook step 1
Immediate response (0-24 h)
- Patch RouterOS to the fixed branches: 6.49.21 (Long-term), 7.23.4 (Long-term), or 7.24.2 (Stable). Deploy via Winbox, WebFig or /system package update, then reboot during a planned window.
- Disable the btest service until patch state is confirmed: /tool bandwidth-server set enabled=no. If operationally required, enforce authenticate=yes and restrict allocate-udp-ports-from.
- Add perimeter ACLs blocking inbound TCP/2000 (btest) and associated UDP traffic on WAN and management interfaces: /ip firewall filter add chain=input protocol=tcp dst-port=2000 action=drop in-interface-list=WAN, mirror for UDP.
- Inventory all internet-exposed MikroTik devices (Shodan, internal scan for TCP/2000, TCP/8291 Winbox, TCP/22, TCP/80, TCP/443) and prioritise CPE/CE routers, site-to-site VPN endpoints and ISP edge devices.
- Post-patch, review unauthenticated services: run /ip service print and disable or scope api, api-ssl, telnet, ftp, www to the management VLAN only.
02
Runbook step 2
Mitigation layers
- Network segmentation: expose the RouterOS management plane only over a dedicated out-of-band VLAN; never expose btest to the WAN under any circumstances.
- On-device firewall rule: /ip firewall filter add chain=input in-interface-list=!LAN protocol=tcp dst-port=2000 action=drop comment="CVE-2026-67277 btest" and equivalent for UDP.
- IPS/perimeter: tune Suricata/Snort to flag inbound TCP/2000 sessions matching the RouterOS btest protocol fingerprint; drop unsolicited UDP toward MikroTik devices at the perimeter firewall.
- IAM hardening: remove or rename the default admin account, enforce strong credentials, and allow-list Winbox/SSH sources via /ip service set winbox address=10.0.0.0/24.
- Monitoring uplift: enable SNMP and Syslog export to a central SIEM so reboots and kernel panics are reliably correlated.
- Lift the change-freeze on affected devices only after verifying the running build via /system resource print meets or exceeds the fixed version.
03
Runbook step 3
Detection rules
- Syslog/SIEM: hunt for unexpected reboots citing "kernel failure", "watchdog", or silent reconnects; correlate with inbound TCP/2000 within the preceding 60 s. KQL shape: Syslog | where SyslogMessage has_any ("router rebooted","kernel panic","watchdog") | join kind=inner (Zeek_conn | where id_resp_p == 2000) on $left.Computer == $right.id_resp_h.
- Zeek/Suricata: conn.log records with resp_p=2000 and a history field lacking a complete auth handshake pattern; also flag unusually large fragment chains (frag events) originating from RouterOS devices.
- NetFlow: anomaly rule on sudden UDP egress spikes with heavily fragmented packets from MikroTik management IPs — a signature of the integer-underflow trigger and kernel buffer leak.
- Sigma shape (network logs): detection: selection: dst_port: 2000 protocol: tcp auth_state: unauthenticated condition: selection, mapped against existing MikroTik API/btest parsers.
- SNMP polling: track hrSystemUptime across all RouterOS devices at 5-minute intervals; multiple uptime resets within 24 h should raise a high-severity alert.

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2 NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management. Read in glossary: Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
CRA The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates. Read in glossary: Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
ISO/IEC 27001 ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security. Read in glossary: Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

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)

Source: pwn.watch, CISA KEV Catalog, ENISA EUVD, NVD (NIST), cvelistv5, BSI CSAF, BSI WID Portal

Affected products

The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

Affected products
		Affected versions	Fixed in
Mikrotik	RouterOS	`6.0.0 – < 6.49.21` `7.24 – < 7.24.2` `7.0.0 – < 7.23.4`	`6.49.21` `7.24.2` `7.23.4`
MikroTik	RouterOS	`< 7.24.2` `< 7.23.4` `< 6.49.21` `<7.25 beta 3`	`7.24.2` `7.23.4` `6.49.21` —

Vendors and products

MikroTik MikroTik RouterOS

Affected operating systems

Affected operating systems

Other	mikrotik	routeros	—

Weakness classes (CWE)

CWE-306Missing Authentication for Critical Function
Base
The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.
Entry at MITRE CWE-306

Public exploit references

Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

Public exploit references

CISA KEV Catalog	CISA Known Exploited Vulnerability (opens in a new tab)cisa.gov	actively exploited	10.09.2026

References & sources

cert.plen/posts/2026/09/mikrotik-routeros-cveeuvd, Third-party advisory
cert.plen/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-…euvd, Technical description
npratley.netreversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-w…euvd, Exploit
mikrotik.comMikroTik RouterOS — CVE-2026-67277euvd, Vendor advisory, pwn-watch
forum.mikrotik.comt/6-49-21-long-term-is-released/272802euvd, Release notes
forum.mikrotik.comt/7-23-4-long-term-is-released/272801euvd, Release notes
forum.mikrotik.comt/7-24-2-stable-is-released/272800euvd, Release notes
cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2026-67277government-resource
pwn.watchpwn.watch: MikroTik RouterOS: MikroTik RouterOS Improper Neutralization of Argument Delimiters in a Command Vulnerabilitypwn-watch
mikrotik.comMikroTik RouterOS — CVE-2026-86060pwn-watch
NVD (NIST)NVD: CVE-2026-86060pwn-watch
NVD (NIST)NVD: CVE-2026-67277pwn-watch
NVD (NIST)NVD: CVE-2026-67279pwn-watch
cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

11.09.2026Initial analysis by NVDNVD

Newly listed as affected:

MikroTik RouterOS (6.0 – before 6.49.21; 7.0 – before 7.23.4; 7.24 – before 7.24.2)

CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H

New references:

and 4 more references

Show 10 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
CVSS	added	—	AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
Product configuration	added	—	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
Reference type	added	—	CERT.PL: https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve Types: Third Party Advisory
Reference type	added	—	CERT.PL: https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/ Types: Mitigation, Third Party Advisory
Reference type	added	—	CERT.PL: https://forum.mikrotik.com/t/6-49-21-long-term-is-released/272802 Types: Release Notes
Reference type	added	—	CERT.PL: https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801 Types: Release Notes
Reference type	added	—	CERT.PL: https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800 Types: Release Notes
Reference type	added	—	CERT.PL: https://mikrotik.com/supportsec/september-2026-vulnerability/ Types: Vendor Advisory
Reference type	added	—	CERT.PL: https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/ Types: Exploit, Third Party Advisory
Reference type	added	—	CISA-ADP: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-67277 Types: US Government Resource

Source identifier: nvd@nist.gov

11.09.2026Record modifiedCISA ADP

CISA assessment (SSVC): exploitation: active, automatable: yes

Show the original change

Individual changes of this event as published by NVD
Type	Action	Before	After
SSVC assessment	changed	{"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"}

Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

10.09.2026CISA KEV entry updated9119a7d8…
4 individual changes: Date Added, Due Date, Required Action, Vulnerability Name
Show 4 original changes
Individual changes of this event as published by NVD
Type Action Before After
Date Added added
—
2026-09-10
Due Date added
—
2026-09-10
Required Action added
—
2026-09-10
Vulnerability Name added
—
2026-09-10
Source identifier: 9119a7d8-5eab-497f-8521-727c672e3725

Individual changes of this event as published by NVD
Type	Action	Before	After
Date Added	added	—	2026-09-10
Due Date	added	—	2026-09-10
Required Action	added	—	2026-09-10
Vulnerability Name	added	—	2026-09-10

10.09.2026Record modifiedCISA ADP

CISA assessment (SSVC): exploitation: active, automatable: yes

New references:

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-67277

Show 2 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-67277
SSVC assessment	changed	{"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"}

Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

09.09.2026Record modifiedCISA ADP

CISA assessment (SSVC): exploitation: none known, automatable: yes

Show the original change

Individual changes of this event as published by NVD
Type	Action	Before	After
SSVC assessment	changed	{"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"}

Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

Show 3 older changes

08.09.2026Record modifiedCISA ADP

CISA assessment (SSVC): exploitation: none known, automatable: no

Show the original change

Individual changes of this event as published by NVD
Type	Action	Before	After
SSVC assessment	added	—	{"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"}

Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

05.09.2026Record modifiedcert.pl

Description added or changed

Show the original change

Individual changes of this event as published by NVD
Type	Action	Before	After
Description	changed	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)

Source identifier: cvd@cert.pl

05.09.2026Receivedcert.pl

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

Weakness type: CWE-306

Description added or changed

New references:

and 3 more references

Show 11 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Description	added	—	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)
CVSS	added	—	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
Weakness type (CWE)	added	—	CWE-306
Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/67xxx/CVE-2026-67277.json">CVE-2026-67277</a>
Reference	added	—	https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve
Reference	added	—	https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/
Reference	added	—	https://forum.mikrotik.com/t/6-49-21-long-term-is-released/272802
Reference	added	—	https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801
Reference	added	—	https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800
Reference	added	—	https://mikrotik.com/supportsec/september-2026-vulnerability/
Reference	added	—	https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/

Source identifier: cvd@cert.pl

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What is affected, what to do

Metrics

Response and mitigation

Prioritisation rationale

Immediate response (0-24 h)

Mitigation layers

Detection rules

Detection rules

Classification under NIS2 and CRA

Description

Affected products

Vendors and products

Affected operating systems

Weakness classes (CWE)

Public exploit references

References & sources

Changes to this CVE