CVE-2026-67278 — TLS server impersonation possible in Mikrotik RouterOS
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. This issue affects only 7.x branch was fixed in versions: 7.23.6 (Long-term) and 7.24.3 (Stable). Releases 7.23.4 and 7.24.2 included an incomplete fix.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- Technical severity (critical)+10
- CISA SSVC: exploitation "poc"+5
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented mitigation — cert.pl (NIST National Vulnerability Database)
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Mikrotik Routeros).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- Apply the documented mitigations until a definitive fix is available.
- Search available logs for exploit probes matching the vulnerability class (cryptography), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 6.3 | CVSS 4.0 | Medium | — | — | cvd@cert.pl via NIST National Vulnerability Database |
| 6.3 | CVSS 4.0 | Medium | — | — | CERT-PL via CVE Program (cve.org) e CISA ADP |
| 9.1 | CVSS 3.1 | Critical | 3.9 | 5.2 | nvd@nist.gov via NIST National Vulnerability Database |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N (score shown at the top: nvd@nist.gov) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
- Check TLS negotiations and unexpected certificates in the component’s traffic.
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · mikrotik/routeros
- SSVC assessment updated
- Record published
- Fix documented
- CVSS changed · 9.1
- Source status changed · → Analyzed
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 15, 2026 – Oct 15, 2026
References
6 on the record
- mikrotik.com/supportsec/september-2026-vulnerability/
- cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros-actively-exploi
- cert.pl/en/posts/2026/09/mikrotik-routeros-cve
- forum.mikrotik.com/t/7-24-3-stable-is-released/273138
- forum.mikrotik.com/t/7-23-6-long-term-is-released/273139
- npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt
Elsewhere on this site
Related CVEs (same products)
- High CVE-2026-103903 MikroTik RouterOS WinBox split-principal authentication bypass allows privilege escalation 3d
- Critical CVE-2026-84411 MikroTik RouterOS Integer Underflow 13d
- High CVE-2026-89028 MikroTik RouterOS < 7.24 Heap Corruption via SMB1 SessionSetupAndX 29d
- Medium CVE-2026-56719 MikroTik RouterOS < 7.24 Out-of-Bounds Read via SMB1 SessionSetupAndX 29d
- Medium CVE-2026-89020 MikroTik RouterOS Stack Buffer Overflow via TFTP URL Path Sep 14, 2026
- Medium CVE-2026-89021 MikroTik RouterOS Path Traversal via Container OCI/tar Image Extraction Sep 14, 2026
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No FIRST EPSS score.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-67278 is "TLS server impersonation possible in Mikrotik RouterOS", rated Critical. It affects Routeros (Mikrotik); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.1 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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