dbcve.org
RouterosOperating system · Mikrotik

CVE-2019-3977

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 6.45.6 Stable, RouterOS 6.44.5 Long-term, and below insufficiently validate where upgrade packages are download from when using the autoupgrade feature. Therefore, a remote attacker can trick the router into "upgrading" to an older version of RouterOS and possibly reseting all the system's usernames and passwords.

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 autoupgrade feature insufficiently validates the source of upgrade packages, allowing a remote attacker to perform a man-in-the-middle attack and redirect the router to download a malicious or older version of RouterOS. This can result in a system downgrade that resets all usernames and passwords, granting the attacker administrative access.

MitigationUpgrade RouterOS to a version beyond 6.45.6 Stable or 6.44.5 Long-term, and if possible, disable the autoupgrade feature and use manual upgrades from verified MikroTik sources.

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 installed RouterOS version
    Run /system resource print in RouterOS CLI or Winbox to view the current RouterOS version number
    Affected if Version is 6.44.5 or lower, or 6.45.6 or lower
  2. Verify autoupgrade feature is enabled
    Run /system package autoupgrade print or /system upgrade check-for-updates in RouterOS CLI to see if automatic upgrades are configured
    Affected if Autoupgrade or automatic check-for-updates is enabled and pointing to default or untrusted sources
  3. Review upgrade package source settings
    Run /system upgrade and examine any configured upgrade channels or custom download URLs
    Affected if Non-MikroTik or untrusted custom upgrade sources are configured, or the default MikroTik upgrade source is used

A router is affected if it runs RouterOS version 6.44.5 or below, or 6.45.6 or below, AND has the autoupgrade or automatic update check feature enabled

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 version beyond 6.45.6 Stable or 6.44.5 Long-term, and if possible, disable the autoupgrade feature and use manual upgrades from verified MikroTik sources.

Fix this in Routeros Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2019-3977 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2019-3977 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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