{"id":"CVE-2026-67277","published":"2026-09-05T20:17:18Z","modified":"2026-09-11T12:52:29Z","title":"MikroTik RouterOS Missing Authentication for Critical Function Vulnerability","vendor":"MikroTik","product":"RouterOS","tier":"core","eol":null,"description":{"text":"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.\n\n\n\nThis issue was fixed in versions: 6.49.21 (Long-term), 7.23.4 (Long-term) and 7.24.2 (Stable)","provenance":"source","from":"NVD"},"summary":{"text":"MikroTik RouterOS accepts a related btest connection before the corresponding primary session has finished authenticating, and the btest handling also contains an unchecked packet-size interval that causes an integer underflow. An unauthenticated network-reachable client can exploit this by starting an IPv4 UDP test, and when the random-data option is disabled, it can leak uninitialized kernel packet buffer contents and, through the packet-size flaw, trigger a restart of the RouterOS kernel.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-29T13:44:16Z"},"cvss":{"score":8.2,"severity":"HIGH","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H","provenance":"source","from":"NVD"},"epss":{"score":0.0156,"percentile":0.75209,"date":"2026-10-30","provenance":"source"},"kev":{"dateAdded":"2026-09-10","dueDate":"2026-09-13","ransomware":false,"requiredAction":"Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.","notes":"https://mikrotik.com/supportsec/september-2026-vulnerability/ ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2026-67277","provenance":"source"},"vulncheckKev":{"dateAdded":"2026-09-05","exploitedFirstSeen":"2026-09-05","ransomware":false,"evidence":[{"url":"https://euvd.enisa.europa.eu/enisa/EUVD-2026-72025","date":"2026-09-05"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2026-09-10"}],"evidenceTotal":2,"provenance":"source"},"exploited":true,"otx":{"pulseCount":30,"pulses":[{"name":"Actively_Exploited_Kev | Oct 31, 2026","url":"https://otx.alienvault.com/pulse/6ae4aefab0c2191cecd41862","created":"2026-10-30"},{"name":"Actively_Exploited_Kev | Oct 30, 2026","url":"https://otx.alienvault.com/pulse/6ae35d889ea92b4ce19c2680","created":"2026-10-29"},{"name":"Actively_Exploited_Kev | Oct 29, 2026","url":"https://otx.alienvault.com/pulse/6ae20c1db17e7057ae7d9ad1","created":"2026-10-28"},{"name":"Actively_Exploited_Kev | Oct 28, 2026","url":"https://otx.alienvault.com/pulse/6ae0ba7e0e2a97ff7b218819","created":"2026-10-27"},{"name":"Actively_Exploited_Kev | Oct 27, 2026","url":"https://otx.alienvault.com/pulse/6adf68b85c3e852f3c111d18","created":"2026-10-26"},{"name":"Actively_Exploited_Kev | Oct 24, 2026","url":"https://otx.alienvault.com/pulse/6adb740e397c3ad4799aa4cd","created":"2026-10-23"},{"name":"Actively_Exploited_Kev | Oct 23, 2026","url":"https://otx.alienvault.com/pulse/6ada236fcfba2dfa730ea482","created":"2026-10-22"},{"name":"Actively_Exploited_Kev | Oct 22, 2026","url":"https://otx.alienvault.com/pulse/6ad8d33a077cbb5cab524d80","created":"2026-10-21"},{"name":"Actively_Exploited_Kev | Oct 21, 2026","url":"https://otx.alienvault.com/pulse/6ad78130c4d1ac2be83a8b6d","created":"2026-10-20"},{"name":"Actively_Exploited_Kev | Oct 20, 2026","url":"https://otx.alienvault.com/pulse/6ad62f63c24a405a3423cc13","created":"2026-10-19"}],"provenance":"machine"},"cwes":[{"id":"CWE-306","name":"Missing Authentication for Critical Functionality"}],"references":[{"url":"https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve","tags":["Third Party Advisory"]},{"url":"https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/","tags":["Mitigation","Third Party Advisory"]},{"url":"https://forum.mikrotik.com/t/6-49-21-long-term-is-released/272802","tags":["Release Notes"]},{"url":"https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801","tags":["Release Notes"]},{"url":"https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800","tags":["Release Notes"]},{"url":"https://mikrotik.com/supportsec/september-2026-vulnerability/","tags":["Vendor Advisory"]},{"url":"https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/","tags":["Exploit","Third Party Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-67277","tags":["US Government Resource"]}],"techniques":[{"id":"T1190","name":"Exploit Public-Facing Application","tactics":["initial-access"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: Unauthenticated network service exploitation via btest","mappingType":"exploitation_technique","evidence":[{"from":"description","quote":"An unauthenticated client can use this state to start an IPv4 UDP test","start":117,"end":187}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"},{"id":"T1005","name":"Data from Local System","tactics":["collection"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: Leaks uninitialized kernel memory contents to attacker","mappingType":"primary_impact","evidence":[{"from":"description","quote":"the sender transmits an uninitialized tail from a kernel packet buffer","start":215,"end":285}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"},{"id":"T1499.004","name":"Application or System Exploitation","tactics":["impact"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: Kernel restart causes application/system denial of service","mappingType":"primary_impact","evidence":[{"from":"description","quote":"can restart the RouterOS kernel","start":415,"end":446}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2026-72025","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-72025","exploited":true,"exploitedSince":"2026-09-05","provenance":"source"},"exploits":[],"exploitSources":null,"exploitRefs":["https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/"],"flow":[{"stage":"exploitation","techniques":["T1190"],"provenance":"ai"},{"stage":"primary","techniques":["T1005","T1499.004"],"provenance":"ai"}],"timeline":[{"date":"2026-09-05","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-67277","provenance":"source"},{"date":"2026-09-05","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://euvd.enisa.europa.eu/enisa/EUVD-2026-72025","provenance":"source"},{"date":"2026-09-05","kind":"euvd-exploited","label":"ENISA EUVD: exploited","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-72025","provenance":"source"},{"date":"2026-09-10","kind":"kev","label":"Added to CISA KEV","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","provenance":"source"}],"speed":{"daysToPublicExploit":null,"firstExploitFrom":null,"daysToKev":5},"priority":{"score":73.8,"factors":[{"name":"In a KEV catalog","points":35.0,"detail":"listed in CISA KEV and VulnCheck KEV"},{"name":"Recent KEV listing","points":10.0,"detail":"added 56 days ago"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":15.04,"detail":"percentile 0.7521"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":5.0,"detail":"1 NVD reference tagged Exploit"},{"name":"Mentioned in OTX pulses","points":3.0,"detail":"30 pulses"},{"name":"CVSS severity","points":5.74,"detail":"base score 8.2"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]}}