CVE-2020-1666
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 · uneditedThe system console configuration option 'log-out-on-disconnect' In Juniper Networks Junos OS Evolved fails to log out an active CLI session when the console cable is disconnected. This could allow a malicious attacker with physical access to the console the ability to resume a previous interactive session and possibly gain administrative privileges. This issue affects all Juniper Networks Junos OS Evolved versions after 18.4R1-EVO, prior to 20.2R1-EVO.
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 confidenceIn Junos OS Evolved, the 'log-out-on-disconnect' console configuration option fails to properly terminate an active CLI session when the physical console cable is disconnected. This leaves the session in a suspended but accessible state, allowing an attacker with physical console access to resume the previous interactive session and potentially obtain administrative privileges.
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= 19.2= 19.3= 19.4= 20.1CVSS 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
- Physical
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:P/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
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 checksWork through these to decide whether this CVE applies to you.
-
Check Junos OS Evolved versionRun 'show version' or 'show version extensive' to display the installed Junos OS Evolved versionAffected if The version displayed is 19.2, 19.3, 19.4, or 20.1 (any of the listed affected versions)
-
Verify console configuration existsRun 'show configuration system ports console' to view the console port configurationAffected if Console configuration is present and 'log-out-on-disconnect' is set (the vulnerability manifests when this option is configured but fails to work properly)
-
Check for active or suspended CLI sessionsRun 'show system connections' or 'show system users' to list active CLI sessions, noting any sessions marked as suspended or disconnectedAffected if There are suspended or disconnected CLI sessions that remain accessible after console cable disconnection
-
Inspect session management settingsRun 'show configuration system | display set | match session' to check session-related configuration optionsAffected if Session timeout or termination settings are configured but console disconnect behavior still allows session resumption
You are affected if your Junos OS Evolved version is 19.2, 19.3, 19.4, or 20.1 AND the console 'log-out-on-disconnect' option is configured but fails to terminate sessions when the physical console cable is disconnected, leaving suspended sessions that can be resumed.
Generated from the published advisory. Verify against your own configuration.
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 dataUpgrade to Junos OS Evolved 20.2R1-EVO or later where the issue is resolved. As an interim control, enforce strict physical access restrictions to console ports and consider disabling automatic session resumption features.
- Consultation3.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,168.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-1666 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-1666 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
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.
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.
- 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