CVE-2026-67277
MikroTik · published 2026-09-05
Source record Collected from the National Vulnerability Database (NVD)
CISA Known Exploited Vulnerabilities
CISA lists this CVE as known exploited (added 2026-09-10).
- CISA's name for it: MikroTik RouterOS Missing Authentication for Critical Function Vulnerability
- CISA's description: MikroTik RouterOS contains a missing authentication for critical function vulnerability which allows kernel memory disclosure and denial of service in the btest service.
- Known ransomware campaign use, per CISA: Unknown
Source: CISA KEV catalog (CC0 1.0).
Description
Description by CERT.PL via the CVE Program.
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)
Filed by CERT.PL; not a statement by MikroTik.
Status at the source
- NVD status: Analyzed
Affected products, as the source lists them
| Vendor | Product | Versions |
|---|---|---|
| Mikrotik | RouterOS | 7.24 – before 7.24.2: affected 7.0.0 – before 7.23.4: affected 6.0.0 – before 6.49.21: affected |
Products named in NVD's CPE match criteria (1)
cpe:2.3:o:mikrotik:routeros:*:*:*:*:*:*:*:*
DeSpy has not checked any unit, hardware revision or firmware. A product missing here is not a statement that it is unaffected.
Scores, as their sources published them
- CVSS 4.0: 8.8 HIGH — as published by CERT.PL (Secondary)
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - CVSS 3.1: 8.2 HIGH — as published by NIST (Primary)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H - SSVC — CISA's assessment (SSVC 2.0.3, CISA Coordinator): Exploitation: active · Automatable: yes · Technical impact: partial
DeSpy does not score records. These are the sources' own values.
Weaknesses
Sources
References the source lists
- 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
Source dates: published 2026-09-05, last changed 2026-09-11. DeSpy's copy of this version is dated 2026-09-28.
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