CVE-2026-16347 — Improper restriction of excessive authentication attempts in MikroTik RouterOS and Cloud Hosted Router
MikroTik RouterOS contains a weakness in its API authentication handling that lacks effective safeguards against excessive login attempts. The system does not enforce meaningful rate-limiting, account lockout, or source-based restrictions, allowing repeated authentication failures to proceed without defensive response. In some versions, a fixed per-connection delay is present, but it can be bypassed through concurrent sessions, resulting in continued high-volume attempts. This deficiency increases the risk that an attacker could eventually obtain valid credentials and gain unauthorized access to administrative services.
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 (high)+6
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.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
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 Cloud Hosted Router, Mikrotik Routeros).
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- Search available logs for exploit probes matching the vulnerability class (authentication), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Mikrotik | Cloud Hosted Router | version All versions | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Mikrotik | Routeros | version All versions | Vulnerable | CVE Program (cve.org) e CISA ADP |
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 |
|---|---|---|---|---|---|
| 8.7 | CVSS 4.0 | High | — | — | ics-cert@hq.dhs.gov via NIST National Vulnerability Database |
| 8.7 | CVSS 4.0 | High | — | — | icscert via CVE Program (cve.org) e CISA ADP |
| 8.8 | CVSS 3.1 | High | 2.8 | 5.9 | ics-cert@hq.dhs.gov via NIST National Vulnerability Database |
| 8.8 | CVSS 3.1 | High | — | — | icscert via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: ics-cert@hq.dhs.gov) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
CWE-307 · Improper Restriction of Excessive Authentication Attempts
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Review authentication logs: logins without MFA, anomalous sessions and recently created accounts.
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · mikrotik/routeros, mikrotik/cloud hosted router
- SSVC assessment updated
- Record published
- CVSS changed · 8.8
- Source status changed · → Deferred
- 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
1 on the record
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 fixed version, patch or mitigation documented.
- 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-2026-16347 is "Improper restriction of excessive authentication attempts in MikroTik RouterOS and Cloud Hosted Router", rated High. It affects Cloud Hosted Router (Mikrotik); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.8 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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