MSRXCVE-2026-67277
CVE-2026-67277
MikroTik RouterOS Missing Authentication for Critical Function Vulnerability
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.
CVSS 4.0 · CNA · cert.pl
chance of exploitation in the next 30 days (EPSS; higher than 75% of CVEs)
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)
Scores
Affected products
- mikrotik routeros: ≥ 6.0, < 6.49.21; ≥ 7.0, < 7.23.4; ≥ 7.24, < 7.24.2
Weakness: CWE-306
8 references (advisories, patches, write-ups)
- 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: NVD, CVE.org, FIRST EPSS. Missing ones did not answer or have no record yet.