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RouterosOperating system · Mikrotik

CVE-2019-3979

HIGH · 7.5 CVSS v3.1 Published 2019-10-29
Fix available
A fix is available. Upgrade to after 6.45.6 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
RouterOS versions 6.45.6 Stable, 6.44.5 Long-term, and below are vulnerable to a DNS unrelated data attack. The router adds all A records to its DNS cache even when the records are unrelated to the domain that was queried. Therefore, a remote attacker controlled DNS server can poison the router's DNS cache via malicious responses with additional and untrue records.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

RouterOS versions 6.45.6 and below contain a DNS cache poisoning vulnerability where the router incorrectly caches all A records from DNS responses, including records unrelated to the queried domain. A remote attacker controlling a malicious DNS server can inject false DNS records into the router's cache, enabling subsequent traffic redirection to attacker-controlled infrastructure.

MitigationUpgrade RouterOS to a patched version. Alternatively, restrict DNS servers to trusted internal or secured DNS infrastructure, and consider implementing DNSSEC validation.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
RouterosOperating system
Affected:<= 6.44.5<= 6.45.6

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check RouterOS version
    Run '/system resource print' or '/system package print' to display the installed RouterOS version
    Affected if Version is 6.44.5 or below, or between 6.44.6 and 6.45.6 (inclusive)
  2. Verify DNS service is enabled
    Run '/ip dns print' to check if the DNS server feature is turned on
    Affected if DNS server is enabled and the router is caching DNS responses
  3. Confirm DNS cache usage
    Run '/ip dns cache print' to inspect the current cached DNS records
    Affected if Cached entries exist, indicating the router is acting as a DNS resolver/cache for clients

The environment is affected if the RouterOS version falls within 6.44.5 or below, or 6.44.6 through 6.45.6, AND the DNS server/cache feature is enabled on the router.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Upgrade available Upgrade to a release after 6.45.6
Interim mitigation

Upgrade RouterOS to a patched version. Alternatively, restrict DNS servers to trusted internal or secured DNS infrastructure, and consider implementing DNSSEC validation.

Fix this in Routeros Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,580
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,128.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2019-3979 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data