# CVE-2026-67277: Kernel memory disclosure and denial of service in MikroTik RouterOS btest service

> CVE-2026-67277: Kernel memory disclosure and denial of service in MikroTik RouterOS btest service. CVSS 8.2 (CVSS 3.1), in CISA KEV.

Canonical: https://rewindex.com/cve/CVE-2026-67277
Last updated: 2026-09-11T12:52:29Z

- Published: 2026-09-05 20:00 UTC · Updated: 2026-09-11 12:52 UTC · Assigner: CERT-PL
- CVSS: 8.2 (CVSS 3.1) · Severity: High · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
- EPSS: 1.6%, 75th percentile (scored 2026-10-25)
- CISA KEV: yes, added 2026-09-10, federal due date 2026-09-13, ransomware use: Unknown
- CWE: CWE-306

## 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)

## 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.

## Affected vendors and products

- Mikrotik: RouterOS

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-67277)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-67277)
- [https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve](https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve)
- [https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/](https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/)
- [https://forum.mikrotik.com/t/6-49-21-long-term-is-released/272802](https://forum.mikrotik.com/t/6-49-21-long-term-is-released/272802)
- [https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801](https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801)
- [https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800](https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800)
- [https://mikrotik.com/supportsec/september-2026-vulnerability/](https://mikrotik.com/supportsec/september-2026-vulnerability/)
- [https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/](https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-67277 · Markdown: https://rewindex.com/cve/CVE-2026-67277.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-67277 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T03:11:07.705Z