High severity8.2CISA KEVNVD Advisory· Published Sep 5, 2026· Updated Sep 11, 2026
CVE-2026-67277
CVE-2026-67277
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)
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected products
2Patches
Vulnerability mechanics
References
8- npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/nvdExploitThird Party Advisory
- cert.pl/en/posts/2026/09/mikrotik-routeros-cvenvdThird Party Advisory
- cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/nvdMitigationThird Party Advisory
- mikrotik.com/supportsec/september-2026-vulnerability/nvdVendor Advisory
- forum.mikrotik.com/t/6-49-21-long-term-is-released/272802nvdRelease Notes
- forum.mikrotik.com/t/7-23-4-long-term-is-released/272801nvdRelease Notes
- forum.mikrotik.com/t/7-24-2-stable-is-released/272800nvdRelease Notes
- www.cisa.gov/known-exploited-vulnerabilities-catalognvdUS Government Resource
News mentions
6- CISA Adds 5 Actively Exploited Artifactory, ScreenConnect, and RouterOS Flaws to KEVThe Hacker News · Sep 12, 2026
- Mikrotik: 2 Actively-Exploited Flaws Added to CISA KEVVypr Intelligence · Sep 10, 2026
- MikroTik Patches Critical Flaws Chained to Hack RoutersSecurityWeek · Sep 8, 2026
- ⚡ Weekly Recap: Chrome 0-Day, Router Hijacks, Coder Supply Chain Attack and MoreThe Hacker News · Sep 7, 2026
- Hackers exploit RouterOS flaws to hijack MikroTik devices without authenticationHelp Net Security · Sep 7, 2026
- CISA Adds Two Known Exploited Vulnerabilities to CatalogCISA Alerts