# CVE-2026-67277

## Summary

- **CVE ID:** CVE-2026-67277
- **Severity:** HIGH
- **CVSS Score:** 8.8 (CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N)
- **CWE:** CWE-306
- **Published:** Sep 5, 2026
- **Last Modified:** Sep 11, 2026

## 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)

## Affected Products

- Mikrotik — RouterOS (7.24)
- Mikrotik — RouterOS (7.0.0)
- Mikrotik — RouterOS (6.0.0)

## References

- [CNA](https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve)
- [CNA](https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/)
- [CNA](https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/)
- [CNA](https://mikrotik.com/supportsec/september-2026-vulnerability/)
- [CNA](https://forum.mikrotik.com/t/6-49-21-long-term-is-released/272802)
- [CNA](https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801)
- [CNA](https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800)
- [CISA-ADP](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-67277)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.87%
- **EPSS Percentile:** 57.0

## Known Exploited Vulnerabilities (KEV)

- **Date Added:** Sep 10, 2026
- **Due Date:** Sep 13, 2026

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-18._