CVE-2017-10621
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 · uneditedA denial of service vulnerability in telnetd service on Juniper Networks Junos OS allows remote unauthenticated attackers to cause a denial of service. Affected Junos OS releases are: 12.1X46 prior to 12.1X46-D71; 12.3X48 prior to 12.3X48-D50; 14.1 prior to 14.1R8-S5, 14.1R9; 14.1X53 prior to 14.1X53-D50; 14.2 prior to 14.2R7-S9, 14.2R8; 15.1 prior to 15.1F2-S16, 15.1F5-S7, 15.1F6-S6, 15.1R5-S2, 15.1R6; 15.1X49 prior to 15.1X49-D90; 15.1X53 prior to 15.1X53-D47; 16.1 prior to 16.1R4-S1, 16.1R5; 16.2 prior to 16.2R1-S3, 16.2R2;
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 confidenceA denial of service vulnerability exists in the telnetd service on Juniper Networks Junos OS. Remote unauthenticated attackers can exploit this vulnerability to cause the telnetd service to fail, resulting in denial of service. The vulnerability affects multiple Junos OS release trains including 12.1X46, 12.3X48, 14.1, 14.1X53, 14.2, 15.1, 15.1X49, 15.1X53, 16.1, and 16.2.
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= 12.1x45= 12.3x48= 14.1= 14.1x53= 14.2= 15.1= 15.1x49= 15.1x53= 16.1= 16.2CVSS 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
- None
- Availability
- Low
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
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.
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Identify Junos OS versionRun 'show version' or 'show version detail' command on the Juniper device to obtain the installed Junos OS software versionAffected if The displayed version matches one of the affected releases: 12.1X46, 12.3X48, 14.1, 14.1X53, 14.2, 15.1, 15.1X49, 15.1X53, 16.1, or 16.2
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Verify telnetd service is enabledRun 'show system services' or check the configuration for 'system services telnet' under the [edit system services] hierarchy using 'show configuration system services'Affected if Telnet service is configured and enabled in the Junos configuration
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Check telnet access methodRun 'show system connections | match telnet' or review the [edit system services] configuration for telnet-related settingsAffected if Telnet inbound access is permitted to the device
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Confirm vulnerability applicabilityCross-reference: if the device runs an affected Junos version AND telnet service is enabled, the device is vulnerable to CVE-2017-10621Affected if Both conditions are true: vulnerable Junos version AND telnetd service is active
A device is affected if it runs any Junos OS version in the 12.1X46, 12.3X48, 14.1, 14.1X53, 14.2, 15.1, 15.1X49, 15.1X53, 16.1, or 16.2 release trains and has the telnetd service enabled.
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 Junos OS to the specified fixed versions (e.g., 12.1X46-D71, 12.3X48-D50, 14.1R8-S5, etc.). As a compensating control, disable telnetd service if not required and use SSH for administrative access.
- Consultation6.0 h
- Implementation12.0 h
- Testing6.0 h
- Review / QA4.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2017-10621 — 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-2017-10621 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
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- Version or environment caveats, and links to real fixes
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