Summary
generated automatically from NVD dataMikroTik RouterOS lets an unauthenticated client open a "related" btest connection before the primary session has finished authenticating, which allows an IPv4 UDP test to be started. With "random-data=false", the sender can leak an uninitialized tail of a kernel packet buffer, and an unchecked inverted packet-size interval triggers an unsigned integer underflow that produces oversized fragmented output and can restart the kernel. It is rated 8.2 (HIGH, CVSS v3.1), is listed in the CISA KEV catalog, and the description names fixes in 6.49.21, 7.23.4 and 7.24.2.
NVD 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)
⚠️ Actively exploited — CISA KEV
This CVE was added to CISA's Known Exploited Vulnerabilities catalog on 2026-09-10. It is confirmed exploited in the wild and must be patched as a priority.
Remediation deadline (US federal agencies): 2026-09-13
EPSS · FIRST.org
1.6%probability of exploitation in the next 30 days
Higher than 74% of scored CVEs
EPSS (Exploit Prediction Scoring System) estimates, from observed exploitation activity, how likely a CVE is to be exploited in the next 30 days. It complements CVSS, which measures severity, not likelihood. Score of 2026-10-19, recomputed daily by FIRST.org.
In-depth analysis on cveo.tech
We've published a detailed analysis of this CVE — exploitation, IOCs and mitigation.
CVSS v3.1 Score
Information
- Published
- 5 sept. 2026
- Updated
- 11 sept. 2026
- Status
- Analyzed
- Source
- cvd@cert.pl
Affected products
Weaknesses (CWE)
References (8)
- https://cert.pl/en/posts/2026/09/mikrotik-routeros-cveThird Party Advisory
- https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/MitigationThird Party Advisory
- https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/ExploitThird Party Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-67277US Government Resource
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