{"id":"CVE-2026-67278","aliases":["EUVD-2026-72026","GHSA-cq44-x9vf-fpqg"],"status":"published","title":"TLS server impersonation possible in Mikrotik RouterOS","description":"MikroTik RouterOS accepts malformed RSA/PKCS#1 v1.5 signatures across RSA-based services, including TLS/X.509 certificate validation and SSH host-key authentication. Because its trust store includes an e=3 root CA, an attacker controlling or redirecting an outbound RouterOS TLS connection can use the root’s public certificate - without its private key - to forge a trusted intermediate and issue certificates for arbitrary hostnames, enabling TLS server impersonation. The same permissive verification also undermines RSA-based SSH authentication.\n\n\n\nThis issue affects only 7.x branch was fixed in versions: 7.23.6 (Long-term) and 7.24.3 (Stable).\nReleases 7.23.4 and 7.24.2 included an incomplete fix.","severity":{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00261,"percentile":0.18001,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-347"],"published":"2026-09-05T20:00:57Z","modified":"2026-09-25T15:32:30Z","products":[{"vendor":"mikrotik","product":"routeros"}],"references":[{"url":"https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve","tags":["third-party-advisory","Third Party Advisory"]},{"url":"https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited/","tags":["technical-description","Mitigation","Third Party Advisory"]},{"url":"https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/","tags":["exploit","Exploit","Third Party Advisory"]},{"url":"https://mikrotik.com/supportsec/september-2026-vulnerability/","tags":["vendor-advisory","Vendor Advisory"]},{"url":"https://forum.mikrotik.com/t/7-23-6-long-term-is-released/273139","tags":["release-notes","Release Notes"]},{"url":"https://forum.mikrotik.com/t/7-24-3-stable-is-released/273138","tags":["release-notes","Release Notes"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-67278"},{"url":"https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploited"},{"url":"https://forum.mikrotik.com/t/6-49-21-long-term-is-released/272802"},{"url":"https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801"},{"url":"https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800"},{"url":"https://mikrotik.com/supportsec/september-2026-vulnerability"},{"url":"https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain"},{"url":"https://github.com/advisories/GHSA-cq44-x9vf-fpqg"}],"sources":{"cve":[{"id":"CVE-2026-67278","title":"TLS server impersonation possible in Mikrotik RouterOS","description":"MikroTik RouterOS accepts malformed RSA/PKCS#1 v1.5 signatures across RSA-based services, including TLS/X.509 certificate validation and SSH host-key authentication. Because its trust store includes an e=3 root CA, an attacker controlling or redirecting an outbound RouterOS TLS connection can use the root’s public certificate - without its private key - to forge a trusted intermediate and issue certificates for arbitrary hostnames, enabling TLS server impersonation. The same permissive verification also undermines RSA-based SSH authentication.\n\n\n\nThis issue affects only 7.x branch was fixed in versions: 7.23.6 (Long-term) and 7.24.3 (Stable).\nReleases 7.23.4 and 7.24.2 included an incomplete fix.","status":"published","published":"2026-09-05T20:00:57.258Z","modified":"2026-09-17T14:20:12.715Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium","assessor":"cna"}],"cwes":["CWE-347"],"updated_at":"2026-11-02T14:20:06.562031Z"}],"euvd":[{"id":"EUVD-2026-72026","description":"MikroTik RouterOS accepts malformed RSA/PKCS#1 v1.5 signatures across RSA-based services, including TLS/X.509 certificate validation and SSH host-key authentication. Because its trust store includes an e=3 root CA, an attacker controlling or redirecting an outbound RouterOS TLS connection can use the root’s public certificate - without its private key - to forge a trusted intermediate and issue certificates for arbitrary hostnames, enabling TLS server impersonation. The same permissive verification also undermines RSA-based SSH authentication.\n\n\n\nThis issue affects only 7.x branch was fixed in versions: 7.23.6 (Long-term) and 7.24.3 (Stable).\nReleases 7.23.4 and 7.24.2 included an incomplete fix.","status":"published","published":"2026-09-05T20:00:57Z","modified":"2026-09-17T14:20:12Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"updated_at":"2026-11-02T17:28:12.076337Z"}],"ghsa":[{"id":"GHSA-cq44-x9vf-fpqg","title":"MikroTik RouterOS accepts malformed RSA/PKCS#1 v1.5 signatures during X.509 validation. Because...","description":"MikroTik RouterOS accepts malformed RSA/PKCS#1 v1.5 signatures during X.509 validation. Because its trust store includes an e=3 root CA, an attacker controlling or redirecting an outbound RouterOS TLS connection can use the root’s public certificate - without its private key - to forge a trusted intermediate and issue certificates for arbitrary hostnames, enabling TLS server impersonation.\n\nThis issue was fixed in versions: 6.49.21 (Long-term), 7.23.4 (Long-term) and 7.24.2 (Stable)","status":"published","published":"2026-09-05T21:31:20Z","modified":"2026-09-25T15:32:30Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/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","level":"medium"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical"}],"cwes":["CWE-347"],"updated_at":"2026-11-02T15:12:27.190195Z"}],"nvd":[{"id":"CVE-2026-67278","description":"MikroTik RouterOS accepts malformed RSA/PKCS#1 v1.5 signatures across RSA-based services, including TLS/X.509 certificate validation and SSH host-key authentication. Because its trust store includes an e=3 root CA, an attacker controlling or redirecting an outbound RouterOS TLS connection can use the root’s public certificate - without its private key - to forge a trusted intermediate and issue certificates for arbitrary hostnames, enabling TLS server impersonation. The same permissive verification also undermines RSA-based SSH authentication.\n\n\n\nThis issue affects only 7.x branch was fixed in versions: 7.23.6 (Long-term) and 7.24.3 (Stable).\nReleases 7.23.4 and 7.24.2 included an incomplete fix.","status":"published","published":"2026-09-05T20:17:18.257Z","modified":"2026-09-25T14:56:04.743Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/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","level":"medium","assessor":"secondary"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical","assessor":"primary"}],"cwes":["CWE-347"],"updated_at":"2026-11-02T14:12:44.082631Z"}]}}