CVE-2026-67277 KEV
8.2
HIGH · CVSS 3.1 · EPSS 1.6% (pctl 74)
Patch first
On CISA KEV — known exploited in the wild, due 2026-09-13.
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)
Scoring
| CVSS | 8.2 (HIGH, v3.1) |
|---|---|
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H |
| EPSS | 1.56% — more likely to be exploited than 74% of all CVEs |
| Weakness | CWE-306 |
| On CISA KEV | yes — remediate by 2026-09-13 |
| Public exploit | none known |
| Published | 2026-09-05 |
| Last modified | 2026-09-11 |
CISA KEV
| Name | MikroTik RouterOS Missing Authentication for Critical Function Vulnerability |
|---|---|
| Added | 2026-09-10 |
| Due | 2026-09-13 |
| Vendor / product | MikroTik / RouterOS |
| Ransomware use | none reported |
Affected (1)
| Vendor | Product |
|---|---|
| mikrotik | routeros |
References
- https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve
- 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/7-23-4-long-term-is-released/272801
- https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800
- https://mikrotik.com/supportsec/september-2026-vulnerability/
- https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-67277
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