CVEs / CVE-2026-67277
CVE-2026-67277: MikroTik RouterOS Missing Authentication for Critical Function Vulnerability
- Known exploited in the CISA KEV catalog since 10 Sep 2026
- high 8.2 CVSS 3.1 (NVD)
- EPSS 1.55% chance of exploitation in the next 30 days, higher than 75% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
MikroTik RouterOS contains a missing authentication for critical function vulnerability which allows kernel memory disclosure and denial of service in the btest service.
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)
Affected and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| Mikrotik RouterOS | from 7.24, before 7.24.2 | 7.24.2 |
| Mikrotik RouterOS | from 7.0.0, before 7.23.4 | 7.23.4 |
| Mikrotik RouterOS | from 6.0.0, before 6.49.21 | 6.49.21 |
Exploitation
| In CISA KEV since | 10 Sep 2026 |
|---|---|
| Due date for US federal agencies | 13 Sep 2026 |
| Used in ransomware campaigns | Unknown |
| 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. |
Severity
| CVSS 3.1 | 8.2 highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:HScored by NVD |
|---|---|
| Weakness | CWE-306 |
References
- CVE-2026-67277 on NVD
- CVE-2026-67277 in the CISA KEV catalog
- https://mikrotik.com/supportsec/september-2026-vulnerability/ (cited by CISA)
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk (cited by CISA)
- https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk (cited by CISA)
- 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
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
This product uses data from the NVD API but is not endorsed or certified by the NVD.